The Scottish comedian went public five years ago to reveal he was suffering from Parkinson’s disease in 2014.
In August, Sir Michael recounted an “awkward dinner” he had shared with the comic in which he said Sir Billy “no longer recognises close friends”.
“I saw him recently – he’s now living in America – and it was very sad because I was presenting him with a prize at an awards ceremony,” Sir Michael recounted on Saturday Morning with James Martin.
“We had an awkward dinner together because I wasn’t quite sure if he knew who I was or not.”
Sir Billy, speaking in Glasgow to promote Billy Connolly’s Ultimate World Tour showing on ITV next month, rebuffed the accusations about the state of his health.
When asked what he thought of Parkinson’s observations, the comic told The Times magazine: “I don’t know. You’d better ask him.”
Sir Billy added: “It was two years since I’d seen him and that occasion was the GQ dinner and I did really well, so what he was talking about I’ll never know.
“He’s been selling funerals [funeral plans] too long.”
Sir Billy continued: “But the thing that got me about it was what if it was true? It’s still a shi**y thing to do. What do you think of Billy Connolly? ‘Oh, he’s f***ed’.”
When asked if he had spoken to Sir Michael since the event, Connolly said: “No. I don’t speak to him normally anyway.”
Sir Billy is shown dancing naked three times during the latest ITV documentary; once in the Arctic circle in 1995, between ancient standing stones in Orkney in 1994 and the Pinnacles in Australia two years later.
Asked how it feels to be back in Glasgow, he said: “It’s lovely too. It reminds me of soup and stew. I remember going to the butchers as a child and they would give you the stewing steak and when it was slightly short they would put a sausage in to make up the weight.
“I was reminded of it in Malta. I have a house in Malta. I was in the supermarket buying some stuff and she didn’t have the right change, so she gave me a KitKat. It reminded me instantly of the sausage.”
Sir Billy says he wants his ashes sprinkled in the Clyde once he dies, rather than at Loch Lomond as he has previously cited.
But the 76-year-old said he isn’t going anywhere just yet.
“That’s a terrible thing, acting your age,” he said.
“You mustn’t act your age. Act some other bugger’s age. You must stay alive.
“That’s imperative. Don’t do what a lot of people do, surrender to old age and start to wear old guys’ clothes.”