A Royal Navy sailor who served on one of the UK’s nuclear-armed submarines has leaked a catalogue of safety concerns that he claims leaves the vessels a “disaster waiting to happen.”

In an open letter published by Wikileaks William McNeilly describes how as a weapons engineer on board HMS Vanguard he witnessed a list of violations of procedure that leave the UK’s nuclear weapons “wide open to attack” and vulnerable to accidents. He adds he was ignored when he tried to pass his concerns up the chain of command.

Among the allegations McNeilly makes are:

The ID and and access cards of personnel are not checked and their belongings not searched before they board the submarines.

A collision between HMS Vanguard and a French submarine was covered up by superiors and crew were threatened with prison sentences if they made the crash public.

Equipment is faulty and in need of repair; “ HMS Vanguard is in the worst of the worst condition.”

Due to overcrowding on the submarine, temporary beds were set up that blocked access to equipment deemed crucial in an emergency.

The missile control and monitoring panel is not always manned as it should be and alarms are so frequent they are sometimes turned off.

Simple rules, such as a ban on personal electronics are not obeyed.

There is “a complete lack of concern for Top Secret information”, with sensitive documents left in plain view and shared with personnel without the appropriate security clearance.

He witnesses a series of avoidable floods and fires, including one fire caused by plastic bags and toilet rolls being left next to heat-generating equipment.

The whistleblower says he felt compelled to make his revelations as “This is bigger than me, it’s bigger than all of us. We are so close to a nuclear disaster it is shocking.”

The Royal Navy rejects McNeilly’s testimony as “subjective and unsubstantiated personal views” and describes him as a “very junior sailor”. It says it has however launched an investigation into his claims as well as their “unauthorised release”.

Police and naval officials have been trying to locate McNeilly and have not said whether or not he would face arrest for violating the Official Secrets Act.