Sir Bruce Forsyth has spent five nights in intensive care after developing a severe chest infection.
The 89-year-old’s manager confirmed to the BBC he had been in hospital since Sunday.
It is not yet known when the former Strictly Come Dancing host will be discharged from hospital, but he could be returning home on Friday.
A friend of Sir Bruce told the Daily Mail the presenter remained “in great spirits”.
In 2015, the presenter underwent keyhole surgery after suffering two aneurysms, which were discovered when tests were carried out following a fall at his Surrey home.
Sir Bruce left Strictly Come Dancing in 2014, having presented it since the first series, but his manager denied reports in October he had retired from the entertainment industry.
Ian Wilson said at the time Sir Bruce was “recuperating from various health issues”, adding: “His sole focus at the moment is to continue getting better and he has made no formal or informal decision about retiring from showbusiness.”
Sir Bruce has not been seen in public recently, and was too frail to attend the funerals of close friends Ronnie Corbett and Sir Terry Wogan last year.
In an interview last October, his wife said the 89-year-old was still having “a bit of a problem moving”.
“He’s in incredible shape mentally but he gets very tired,” she said, adding: “With a little bit of luck he should be back.”