A hospital spokesman confirmed Best, 59, had been admitted to the intensive care unit but said no further details were available at present.
Best underwent a life-saving liver transplant operation at the Cromwell in 2002 after years of heavy drinking.
But barely a year later he was back on the booze despite doctors’ warnings it could be fatal.
In November last year he had a second operation to check on the condition of his liver and afterwards declared himself fit and healthy, vowing he would be around “for a long time, hopefully”.
Since his divorce from wife Alex in April 2004 he has cut an increasingly shambolic figure.
The former Manchester United and Northern
Ireland star was kicked out of Forest Mere health farm in Hampshire, his home for the past two years, in June this year.
In the same month, he was spotted with two black eyes allegedly inflicted by his partner Ros Hollidge.
In August he was again sporting a black eye after he was reportedly beaten up by three men in a pub in Surbiton, Surrey.
Best’s son Calum Best left the hospital just before 3pm. Asked by reporters how his father was, the model said: “He’s okay. He’s stabilised.”
He added that he would be returning to hospital later. Calum was then driven off in a black cab.
Meanwhile, Liverpool footballer Steve Finnan will give evidence at an inquest into the death of a pensioner who was involved in a collision with his car, it emerged yesterday.
Henry Nelson, 81, from Liverpool, suffered serious injuries after he was struck by the defender’s black Range Rover on January 27 this year. He died five weeks later in hospital.
The Irish international was arrested three months later on suspicion of dangerous driving but never charged.
The footballer, who was a member of the heroic Champions League squad, will be called as a witness at the inquest into Mr Nelson’s death at Liverpool Coroner’s Court on November 24.
Finnan, who originally comes from Limerick, started his career at non-league Welling before moving into league football with Birmingham and Notts County.
George’s agent Phil Hughes said he had brought the former footballer to the hospital last Monday suffering from flu-like symptoms including “shortness of breath”.
“He hasn’t left here since. At 12 o’clock last night I got a phone call from hospital. George had asked the doctors to call me and say he was being taken down to intensive care.
“They said there was no need for me to come in at that stage and just to visit in the morning.”
Mr Hughes said the problems had been caused by drugs George was taking for his liver, which had led to problems with his kidneys.
The Manchester United legend was now on drugs for his kidneys which doctors hope will resolve the issues.
Mr Hughes said: “He’s in and out of consciousness. He is very weak and finds it hard to speak.
“The doctors say he’s on the mend, but he still doesn’t look good to me.”
Mr Hughes said it was “hard to say” when George would be out of hospital.
“Hopefully in the next couple of days he’ll be out of intensive care.”
He added that as far as he was aware only himself and Calum had visited George in hospital.
“It’s very stressful for everyone,” he said.