The 83-year-old star said it had happened at more than one royal occasion and during his most recent scare he had to be passed a screwdriver to free himself in time to give a reading at a memorial service.
The former Two Ronnies star also brushed off health fears while appearing on tomorrow night's The Graham Norton Show on BBC1 after a report he was retiring due to illness.
"It was absolute nonsense. It was very annoying. I got a major apology but not matching the size of the error. It was irresponsible."
He said the error had apologised and had made a payment .
He said: "They sent me some booze and plenty of money which I'm dividing among a number of care homes."
Corbett told presenter Norton about his lavatorial disasters, explaining: "I have been trapped in some posh toilets including those in Windsor Castle and Buckingham Palace, and at Victor Spinetti's memorial at St Paul's Covent Garden, I got locked in the loo.
"I had to scream and shout and eventually someone threw a screwdriver over the door and luckily I was out in time for my reading."
The diminutive star also put to rest an urban myth that he had appeared as one of the apes in the opening scenes of movie classic 2001: A Space Odyssey, but said he was had been approached.
"Stanley Kubrick (the film's director) saw me doing a little spot on Sunday Night At The Palladium and said, 'he would be ideal for one of my apes'. I turned it down."
:: The show is broadcast at 10.20pm on Friday April 18.