Margaret Hodge, the minister for Children, came under renewed pressure to quit yesterday amid fresh claims that social services chiefs had expressed concern about her appointment.
Tony Blair gave Ms Hodge his personal backing yesterday as the controversy continued about her record as leader of Islington council during a child sex abuse scandal in the 1980s and 1990s.
Downing Street revealed that the Prime Minister had been "fully aware" of the allegations when he decided to promote her in the recent reshuffle.
Ms Hodge vigorously denied new allegations that she ignored social workers' concerns about paedophiles operating in the London borough.
However, the Conservatives said that her record in local government had "caused several directors of social services and others to refuse to work with her in her new post".
The Independent has learnt that one head of children's services at a London authority has privately attacked Ms Hodge's record, and was scathing about the chaos at Islington. Another social services director at a London council has also been critical.
A spokeswoman for Croydon council said yesterday that Hannah Miller, its social services director, would not comment on suggestions that she was unhappy with the appointment of Ms Hodge.
"Croydon council does not constrain its chief officers from undertaking their professional work on behalf of the authority which, from time to time, will involve exposure to ministers," she said.
Ministers are worried about whether Ms Hodge will survive the media onslaught. Downing Street has decided to weather the storm, but some ministers fear that she may have to "do a Byers" and admit that the controversy is harming her ability to do her job.