Labour is doomed under Gordon Brown's leadership, former party donor Sir Gerry Robinson has said.
Sir Gerry, a businessman who last gave money to Labour in 2005, told BBC News Mr Brown had put it in "probably an impossible position to come back from".
He was one of four Labour backers to tell a newspaper they were reluctant to fund Labour with Mr Brown at the helm.
The party is also facing a financial crisis, with the prospect of repaying millions of pounds in loans made to it by wealthy individuals when Tony Blair was in charge.
The party - which files its annual accounts next week - is relying on support from the big trade unions as it seeks fresh donors.
But Sir Gerry, who has given £70,000 to Labour since 2001, said he would not be contributing any more funds until there was a change of leader.
Oh dear, oh dear... It really couldn't happen to a more useless, spiteful, unpleasant little man, eh?
Health Secretary Alan Johnson hit back at Mr Brown's critics, insisting the prime minister had had a "good year".
Mr Johnson also maintained that oil was actually $3 a barrel, that wind turbines were very useful and that Vesuvius had never exploded and the residents of Pompeii were alive and well.
The prime minister has had a "good year"? What the fuck? Seriously, does Health Secretary Alan Johnson think we are idiots?
You might argue, as NuLabour apparatchiks do, of course, that the upheavals of the last year have not been the Gobblin' King's fault but by no stretch of the imagination has Gordon had a "good year". It started off with near Biblical floods, Foot and Mouth (caused, it was revealed, by the government's incompetence) and Bluetongue pestilence, and the bombings at Glasgow airport; it has carried on with the credit crunch, the oil crisis and house price correction.
May I suggest that somebody check on Health Secretary Alan Johnson's mental health? Because whilst I am no doctor, if you ask me, he gone completely fucking hatstand. Either that, of course, or he is incapable of telling the truth.
Oh, wait, he's a politician...