The next 24 hours will be critical for former footballer George Best's survival, the doctor treating him said last night.

Professor Roger Williams said Best, 59, was stable but had made no significant improvement since he was placed on a ventilator after being struck down by a lung infection.

He said: "He is holding, that's what I can say. His condition really hasn't changed."

But he added: "I would like to have seen some very definite improvement in this last 24 hours. So I think the next 24 hours is going to be critical as to whether he's going to make it or not."

Prof Williams, who oversaw Best's liver transplant in 2002, said the former footballer's family were saying "swear words, good words, bad words, anything to provoke a reaction from him", however, Best remained heavily sedated and was not communicating with those around him.

He said Best's brother and sisters were in the waiting room, hoping for better news and doing everything they could to keep him going.

He said: "The family are very realistic and they are very nice people. They are trying to give him all the support they can."

The former Manchester United and Northern Ireland player was admitted to the hospital on October 1 suffering from flu-like infections.

His health deteriorated rapidly at the beginning of this month when he developed a kidney infection.

However, his condition was thought to be improving until early last Friday when he suffered a severe setback, having developed a lung infection.

He was placed on the ventilator early on Saturday.

Later that day, Best's son, Calum, arrived at the hospital to visit his father.

Phil Hughes, Best's agent, said his two sisters, Barbara and Carol, were also at his bedside as were his two brother-in-laws, Norman and Alan, and his brother Ian.

Calum left the hospital at about 6.10pm. He said: "I would like to thank all the well-wishers, it really means a lot to me and the family."

He was not seen at the hospital yesterday.

Best's elderly father, Dickie, also visited him on Saturday.

Before being transferred into the intensive care department, seriously-ill Best asked Mr Hughes to take a picture of him as a warning about the dangers of excessive drinking.

Looking gaunt and with a yellow pallor due to his malfunctioning liver, alcoholic Best insisted his photo be taken as a deterrent to others.

The picture, which appeared in yesterday's News of the World, shows him lying in his hospital bed with tubes attached to his bruised body.

Mr Hughes told the paper: "George could never beat his drink problem, but he told me, 'I hope my plight can act as a warning to others'."

Best, who had his life-saving liver transplant at the Cromwell, has a well-documented history of alcoholism.

He had been told one more drink could kill him when he underwent the surgery in July 2002 and was criticised by a liver specialist for putting people off organ donation.

Best then caused anger when he embarked on a drinking binge within months of the transplant, despite having vowed to stay dry.

Asked yesterday about the picture in the News of the World, Prof Williams said: "Well we don't expect him to look pink and wonderful, do we?"

He added Best was receiving all kinds of treatment in the intensive care unit including antibiotics, replacement of fluids and clotting factors.

Prof Williams said Best's family were unlikely to be faced with the tough question of deciding whether or not treatment should continue for him.

"I would imagine the situation will resolve itself naturally, that's what normally happens.

"It's not a case of switching off life support."