McNeilly reported a shockingly wide range of problems within the facilities — from food hygiene to alarms on a Trident submarine's missile control station being turned off, so that crew members didn't have to listen to them.
Since being sacked, he has hit out, telling international broadcaster RT:
"I didn't release my report to discredit the Crown [UK state]. I didn't release my report to discredit the Royal Navy. I released my report because safety and security at the site is not being taken seriously. Because it's risk to the people and a risk to the land.
"All you need to get on board is a couple of fake IDs. Terrorist groups like ISIS [Daesh] have already shown they can produce legitimate documents. Thousands of Royal Navy IDs go missing every year as well, so they could come across one. Increasing numbers within the UK have radicalized people, which increases the risk of one of them coming across an ID," he said.
McNeilly said the idea of nuclear deterrence did not stop the war in Afghanistan. "If you get a list of all the disadvantages, it would be huge. You could write books and books on it. Then they have one vague reason for keeping the Trident system. And that one vague reason is they say it's a deterrent.
"Was it a deterrent for the wars we fought recently? Afghanistan? Does it deter the people who were radicalized in Afghanistan? No. All it does is create a target for those people who are radicalized in Afghanistan, so it's not a deterrent for those people, it's an attraction.
"It doesn't deter them because they know we won't use nuclear weapons in their countries. So it doesn't deter them. All it is an attraction to the people who were radicalized to carry out an attack on our homeland that could bring the UK to its knees."
He was speaking to RT ahead of a major anti-Trident rally in London on February 27 to be attended by UK Labour Party leader Jeremy Corbyn, who has pitted his leadership against renewal of the program.
McNeilly told RT: "If the UK gets rid of its nuclear weapons, they’ve still got the deterrent there, they don’t need them. We’re not going to be attacked, we’re not going to be invaded as soon as they go".
"Anyone who thinks we’re going to be invaded as soon as they vote 'no' on Trident’s renewal, they’re insane. Literally insane. Why would anyone invade the UK?"