At the end of a week in which her political position has come under increasing fire, Downing Street officials pointedly refused to voice full support for Ms Harman, triggering fresh speculation at Westminster that she is being "written out of the script".
However, Government sources privately insist that she will be moved to a less demanding ministerial role rather than sacked outright.
The favourite to replace her is Alistair Darling, Chief Secretary to the Treasury, who is regarded as a rising star in the Blair administration and the right pair of hands to deliver Labour's radical reform of the benefits system.
Chancellor Gordon Brown has hitherto resisted pressure to promote Mr Darling out of his department. But Ms Harman's "leak" of details of state funding of child care for low-income families - due to be announced in the Budget on 17 March - has infuriated Treasury ministers who were among her last remaining allies in government.
Ms Harman's disclosure that the Government will announce a pounds 1bn-a-year plan to finance 75 per cent of child care for the low-paid was regarded as a last-ditch attempt to bolster her standing, but it has backfired spectacularly.
A spokesman for the Prime Minister, asked if Tony Blair still had full confidence in his Social Security Secretary, would only nod his head. In fact, Downing Street is widely regarded as the prime source of the string of "Hattie must go" stories appearing in newspapers throughout last week.
Home Secretary Jack Straw, responding to a question about Cabinet colleagues leaking sections of the Budget, this morning admits on GMTV's Sunday programme that there is "a bit of flakiness at the edges" of the Government. "I think we're not doing too badly," he tells interviewer Alastair Stewart. "We're not perfect. We're human."
Other ministers facing the axe in the prospective Easter reshuffle in six weeks' time include David Clark, Chancellor of the Duchy of Lancaster and Gavin Strang at Transport.Reuse content