TRIDENT submarines are plagued by serious security lapses, beset by multiple safety blunders and are "a disaster waiting to happen", according to a nuclear weapons engineer turned whistleblower who is now being hunted by the police.

William McNeilly, who says he was on patrol with HMS Victorious from January to April this year, alleges that the Trident missiles it carries are vulnerable to a terrorist attack that "would kill our people and destroy our land". Infiltrators have "the perfect opportunity to send nuclear warheads crashing down on the UK", he claims.

He has written a detailed 18-page report called The Nuclear Secrets, which claims to lift the lid on the alarming state of the UK's ageing and short-staffed nuclear deterrent. He went absent without leave from the Royal Navy last week, is on the run and expects to be arrested. "This is bigger than me, it's bigger than all of us," he says. "We are so close to a nuclear disaster it is shocking, and yet everybody is accepting the risk to the public. If we don't act now lives could be lost for generations."

The risk was "extremely high", he told the Sunday Herald. "My information comes from good sources and I have no reason to lie. If change isn't made, a nuclear catastrophe almost certainly will happen."

McNeilly's report alleges 30 safety and security flaws on Trident submarines, based at Faslane on the Clyde. They include failures in testing whether missiles could be safely launched, burning toilet rolls starting a fire in a missile compartment, and security passes and bags going unchecked.

He also reports alarms being muted because they went off so often, missile safety procedures being ignored and top secret information left unguarded.

"It's just a matter of time before we're infiltrated by a psychopath or a terrorist," he says. "There were some people that I served with on that patrol who showed clear psychopathic tendencies."

The Royal Navy has launched an investigation into McNeilly's report, and is working with the civilian police to find him. It describes his criticisms as "subjective and unsubstantiated", stressing that submarines never go to sea unless they are completely safe.

The SNP's Westminster leader, Angus Robertson MP, is demanding a full explanation and action to rectify all the failings. "These revelations, if true, are extremely concerning. It reads as a nightmare catalogue of serious safety breaches," he said.

"They add to what appears to be a chaotic, shambolic safety culture on these aged subs. Broken or faulty equipment with no spares leading to slapdash patch-up jobs have no place in the Navy and just shows how utterly stretched it is."

Robertson added: "Failure to follow standard safety procedures is unacceptable in any workplace but on a Trident submarine on patrol it could result in extreme tragedy, not just for those on board but indeed for the entire planet."

McNeilly claims that there was a "massive cover-up" of what happened when HMS Vanguard collided with the French nuclear submarine, Le Triomphant, in the Atlantic in February 2009. He quotes a senior officer who was on Vanguard at the time as saying: "We thought, this is it, we're all going to die."

The crash dislodged high-pressure air (HPA) bottles, he says. "They had to return to base port slowly, because if one of HPA bottle groups exploded it would have created a chain reaction and sent the submarine plummeting to the bottom."

McNeilly also outlines a litany of equipment problems, including a seawater leak, a flooded torpedo compartment and defective toilets. A missile compartment was used as an exercise gym, he alleges, and the submarine speaker system was difficult to understand.

He insists that he has been careful about what he has said publicly in order to avoid prejudicing security. He repeatedly raised concerns with his superiors but they were ignored, he says.

McNeilly, who describes himself as "weapons engineer", is 25 years old, and from Newtownabbey near Belfast. He says he joined the Navy in July 2013, and arrived at Faslane a year ago.

After six months training, according to his account, he went on patrol with HMS Victorious for three months earlier this year.

It is difficult to independently verify all his allegations.

The independent nuclear submarine expert, John Large, concluded McNeilly was credible, though he may have misunderstood some of the

things he saw.

Large said: "Even if he is right about the disorganisation, lack of morale, and sheer foolhardiness of the personnel around him - and the unreliability of the engineered systems - it is likely that the Trident system as a whole will tolerate the misdemeanours, as it's designed to do."

The Royal Navy confirmed that McNeilly was a member of the naval service. "The Navy is concerned for the whereabouts and wellbeing of able seaman McNeilly and is working closely with civilian police to locate him," it said.

His report did not pose any security risk to personnel or operations, it added. "The document contains a number of subjective and unsubstantiated personal views, made by a very junior sailor, with which the naval service completely disagrees."

A Royal Navy spokeswoman stressed that security and nuclear safety were taken extremely seriously. "We are fully investigating both the issue of the unauthorised release of this document and its contents," she said.

"The naval service operates its submarine fleet under the most stringent safety regime and submarines do not go to sea unless they are completely safe to do so."

But John Ainslie, co-ordinator of the Scottish Campaign for Nuclear Disarmament, praised McNeilly. "He is a whistleblower who has revealed that there is a callous disregard for safety and security onboard Trident submarines," he said.

"He should be commended for his action, not hounded by the Royal Navy. He has exposed the fact that Trident is a catastrophe waiting to happen - by accident, an act of terrorism or sabotage."

Edited extract from the dossier of William McNeilly compiled before going into hiding:

'My name is William McNeilly. I am a weapons engineer submariner for the UK's Trident II D5 strategic weapons system. The penalty for releasing this

report will be life prison if I'm lucky.

The worst fear for me isn't prison ... it's the fear of sacrificing everything I have just to warn the public and yet never be heard. My leave expires today. I will be hunted down for not turning up.

When I'm found I will confess and will no longer be able to keep trying to warn the public. This document will enlighten you about the shockingly extreme conditions that our nuclear weapons system is in right now, and has been in the past. I need you to publish this document or send it to someone who will - please, for the safety of the people.

The complete lack of concern for security worries me. The fact is it would have been even easier for me to cause a nuclear catastrophe than to gather information, and gathering information was actually quite simple, due to the amount of ignorance.

We are at war, with a new kind of enemy. The terrorists have infiltrated every nation on our planet. Our nuclear weapons are a target that's wide open to attack. You don't have to be Alexander the Great to see we must adapt our strategies.

The Cold War is over; are we still in a situation where we must invest billions upon billions into a system that puts our citizens at risk? No! We must adapt to the evolving world in order to survive!

I had envisioned a system with strict security and safety. I didn't see how wrong I was until I arrived at HMS Neptune (Faslane). At the gate the guard barely looked at my pass. It's harder to get into most nightclubs.

We headed down the boat. No search at all. It wasn't because we're Royal Navy personnel; it was because that's the standard procedures. Hundreds of contractors go down the boat when it's alongside.

Their equipment isn't searched and they are not patted down. All it takes is someone to bring a bomb on board to commit the worst terrorist attack the UK and the world has ever seen. At a base security brief we were told that thousands of Royal Navy IDs go missing every year. A terrorist can use them, or create counterfeits with them and easily gain access down the submarine.

We went down to missile compartment two deck, set our bags just feet away from the missiles and no-one stopped us. This was our first time on the boat. No-one in the crew knew who we were, but they still didn't stop us. You can carry anything through the security checkpoints without it being checked.

If you've been through airport security after 9/11 you'll have seen how thorough the security is nowadays. If airport security and nuclear weapon security were both compared to prisons, the airport would be Alcatraz and base security would be house arrest.

Seeing the condition of the security and equipment made me more than concerned, for the safety of the people. It was at that point I realised I needed to gather as much safety and security information as I could. My intentions were to make changes by reporting through the chain of command.

I learnt that HMS Vanguard is in the worst of the worst condition. Countless times it tried to sail but had to come back in, forcing the other boats to do extended patrols.

Just weeks after passing out of training I was drafted to HMS Victorious. Day one was a dark, rainy and windy morning. I made it through the checkpoint by keeping my face away from the guards. I didn't show my ID, and I never handed any ID in.

On the first dive there was a loud continuous bang being heard by everyone. It was down the forward starboard side. The next day in the junior rates mess, I heard people complaining about it being ignored.

A problem occurred with the main hydraulic plant. Somehow seawater was getting into it. The amount of actual hydraulic oil in the plant had fallen to 35 per cent. The problem was there until the end of the patrol.

Hydraulics are used to open the muzzle hatches. This defect stopped them from doing a battle readiness test that proves that the muzzle hatches could have opened whilst on patrol, and that, if we needed to, we could have launched missiles.

I could sometimes hear alarms on the missiles control and monitoring position while lying in bed. I later found out that I would have been hearing them more frequently if they didn't mute the console just to avoid listening to the alarms.

One of the watch keepers laughed about how they would deal with any issues. They would deviate from set procedures because the procedures can be "long and winding." If you work on the strategic weapon system you must follow the procedures. Mistakes can be catastrophic.

A mistake was made on the panel in the control room. A small mistake from this position can cause a disaster. None of the electrical isolations that are required to be made were made, creating a high risk of fire in a compartment which contains torpedoes.

A lot of submarines have been lost due to simple accidents. If one simple mistake is made it can be all over. You can find some of the information online but most of it is covered up. It's only a matter of time before one of the Trident submarines is lost.

Everyone who serves on the Trident submarines knows that it was HMS Vanguard that crashed into the French submarine [in the Atlantic in February 2009]. I was talking to a chief who was on the submarine at the time. He said: "We thought, this is it, we're all going to die." He went on to explain what happened. There was a massive cover up of the incident.

There was a fire in the missile compartment, in harbour. The chief said if it had been at sea there would've been about 50 dead bodies on three deck because of the amount of people struggling to find an emergency breathing system.

The fire was caused by the ship's toilet rolls being stacked from deck to deckhead the whole way along four deck (right beside the missiles and firing units). They reckon it was the heat from the cables that caused the fire.

One motor generator was dysfunctional. There were a lot of problems with the electrical generation equipment. Losing power could result in losing the submarine.

The missile compartment four deck has been turned into a gym. There are people sweating their asses off between the missiles, people rowing between a blanket of shit because the sewage system is defective.

Personal electronics should be banned yet the policy isn't enforced. You can bring whatever electronic devices you want on board. Simple rules like no e-cigs and no shaving are also not obeyed.

One time the supervisor was off somewhere and it would've been easy for me to gather top secret information. To the right buyer this information would sell for millions.

The information I have released in this document has been carefully selected. An idiot may say that releasing information about how open to attack we are will invite terrorism and create an increased risk to security. The truth is the threat already exists.

A few of us got to climb inside a nuclear missile, which could have had up to 12 nuclear warheads on it. I climbed the ladder, put half my body inside the missile and had a look around. If any of us had been terrorists we would've been given the perfect opportunity to send nuclear warheads crashing down on the UK.

Luckily none of us were terrorists. However the rate at which people are getting pushed through the system because of manpower shortages is scary. It's just a matter of time before we're infiltrated by a psychopath or a terrorist.

Some of the personalities on board are already alarming. Probably the most worrying is the junior rate whose hobby is killing small animals. He also expressed his interest in watching dark porn. It appeared most people had breaking points at some point on patrol.

At one point I was told the best way to take down a submarine. I'm not going say how here, that's information nobody should talk about. It's disturbing to know that the people serving on these boats are aware of many ways to destroy them from within.

One of the biggest threats we face is suicidal attack from within. There have been suicides onboard, and on an Astute boat we had a shooter kill his own work colleagues [in Southampton in April 2011]. There were some people that I served with who showed clear psychopathic tendencies.

A missile compensation test was carried out three times and it failed three times. Which means the missiles would have been launched on an unstable platform, if they decided to launch. Basically they're endangering the public and spending billions of taxpayers' money for a system so broken it can't even do the tests that prove it works.

Five minutes before leaving the boat for leave I walked into the junior rates' toilets. The whole deck was flooded in a couple inches of brown water. I tried the senior rates' and it was the same. This summed the system up.

Most people know the Trident programme is a disaster waiting to happen, but they never tell the public. You're guaranteed to lose everything, if you talk. Career, money, everything you own, your freedom, contact with family and friends.

I believe it's in the Prime Minister's best interest to pardon me. Prosecuting someone for alerting the people and the government to a major threat isn't a good image for someone who serves the people.

I raised my concerns about the safety and security of the weapon system through the chain of command on multiple occasions. My concern couldn't have been any clearer. Not once did someone even attempt to make a change.

I strongly believe that the Prime Minister and most people that defended Trident have no idea about how dire the situation is. This is not the time to judge on what they did when they didn't know. It's about what they do now that they know.