SUBMARINER William McNeilly has now been traced to a base in Portsmouth after the Trident whistleblower handed himself in to Naval authorities.

Able Seaman McNeilly, 25, went absent without official leave last week after producing an 18-page report detailing safety and security flaws on the Trident submarines based at Faslane.

The Ministry of Defence (MoD) will not confirm his whereabouts, but as reported in the Sunday Herald, the submariner was pictured by a fellow sailor at the HMS Nelson barracks in Portsmouth and posted it on Facebook.

He was initially believed to have been taken to an undisclosed military base in Scotland, and then to have been moved to England on Wednesday.

McNeilly, who is originally from Newtownabbey, County Antrim, said in his report that he is an Engineering Technician Submariner who was on patrol with the Trident submarine HMS Victorious this year.

Published online and also sent to newspapers and journalists, he alleged 30 safety and security flaws including fire risks, leaks and unchecked bags.

He said he raised concerns with senior officers but decided to publish his claims because they were ignored. After releasing the report, he went on the run abroad before reportedly handing himself into the authorities last Monday.

The Royal Navy said it is "continuing to investigate the circumstances" of the report and a defence minister is expected to make a statement to the House of Commons in London on Thursday.

That same evening the SNP's former First Minister, Alex Salmond MP, has secured a debate on McNeilly's allegations in the House of Commons, which will oblige ministers to answer further questions.

The former First Minister said MoD attempts to "brush it all under the carpet" were "profoundly unsatisfactory".

A spokesman from the Royal Navy told the Sunday Herald that an investigation was underway to "inform a decision as to the requirement for further criminal or disciplinary investigation by the police," adding "he is not in custody but is required to remain in the military establishment while investigations are ongoing."

On McNeilly's allegations, an MoD spokesman said: "The Royal Navy continues to investigate this issue and ministers will update Parliament at the earliest opportunity."

Last Sunday, McNeilly posted a statement for his family and friends on Facebook. He said: "I'm just letting you know I'm alive and well."

"What you don't know is, I've been working covertly to eliminate the biggest threat to the UK for about a year...If change isn't made, a nuclear catastrophe almost certainly will happen."

He then went on to detail the problems her learned about the Trident submarines: "A blazing inferno beside the missile and firing units, covered up crash that nearly took down a boat, numerous floods, numerous fires, hundreds of people bringing unchecked bags etc down the boat every week and walking straight past nuclear missiles, IDs not being checked for facial recognition."