An internal report released by the Ministry of Defence (MoD) said the police, fire and ambulance services faced "major difficulties" dealing with a mocked-up motorway pile-up involving a nuclear bomb convoy near Glasgow because they had no help from MoD weapons experts for more than five hours.
At times the response was disorganised, the report said, and there were fierce disputes with ambulance staff over how to handle casualties at the crash site contaminated with radioactivity. One victim was declared dead as a result of "considerable delay".
The exercise was condemned as shambolic by the SNP's Westminster leader and defence spokesman, Angus Robertson MP.
He said: "The level of disorganisation, poor communications and breakdown between so many agencies involved in this test is just breathtaking.
"The report exposes huge safety concerns in the ability, especially of the MoD, to deal with a real nuclear accident. It highlights many potential problems in responding quickly and effectively, and demands questions to be asked of the MoD, which I will be doing at the first available opportunity this week."
The exercise, codenamed Senator, took place in September 2011 and involved more than 1000 people and 21 public agencies, including local authorities, the Scottish Government and the Cabinet Office. It was staged on a naval base at Prestwick Airport in South Ayrshire.
The scenario envisaged a large goods lorry suffering a blowout while travelling north on the M74, near the busy Raith interchange at Bellshill, then crashing into a nuclear weapons carrier. Leaking fuel bursts into flames, and a cloud of radioactivity then starts to spread over Motherwell. A second weapons carrier has to take evasive action and is involved in another collision with a lorry.
Up to 100 people were said to have been contaminated with radioactivity at the scene, seven suffered serious injuries and two were killed. But there was a series of problems dealing with the simulated disaster, according to a report by the MoD's Defence Nuclear Safety Regulator, released under freedom of information.
It took five-and-a-half hours for experts on the MoD's Military Coordinating Authority to get from their base at Abbey Wood in Bristol to the police's emergency control centre in East Kilbride.
"This lack of support created major difficulties for the multi-agency response, which struggled to attain a meaningful understanding of the issues," the report said. It also criticised the refusal of the Scottish Ambulance Service (SAS) to transport two seriously injured people to hospital because they were contaminated with radioactivity. Royal Marines and MoD Police took a rapid decision to "crash the cordon" and take them in military vehicles.
Nukewatch, which monitors the transport of nuclear weapons, warned the flaws highlighted could all increase the risks in the event of a real accident. "This exercise shows that, at the height of the crisis, Scotland would be left to fend for itself by Whitehall in the event of an emergency involving a British nuclear weapon," said the group's Jane Tallents. "Far from being a benign insurance policy keeping the public safe, nuclear weapons actually increase the risks we all face."
Nuclear bombs are transported in heavily guarded road convoys up to six times a year between the Atomic Weapons Establishment at Aldermaston in Berkshire and the Royal Naval Armaments Depot at Coulport on Loch Long in Argyll. The trips are needed to ensure the UK's stockpile of about 200 Trident missile warheads is properly maintained.
The MoD said that since the 2011 exercise, "Some improvements were identified to further enhance procedures and these have since been addressed."