Independent MP Andrew Wilkie

"Inclined" to support the budget's two main money bills ... Andrew Wilkie. Photo: Peter Mathew

SENIOR government ministers are demanding independent MP Andrew Wilkie give a guarantee he will not block supply before negotiating with him on other demands.

Mr Wilkie has raised a federal takeover of the Tasmanian health system - or at least a significant injection of new money - as a new bargaining chip in the wake of Peter Slipper's decision to stand aside while criminal allegations against him are investigated.

''They have demanded an absolute guarantee, either written or verbal,'' sources close to Mr Wilkie said yesterday. Mr Wilkie has said he is ''inclined'' to support the two main money bills of the budget, but reserved the right to knock back any associated measures, a tactic the government expects the Greens to use.

The Prime Minister, Julia Gillard, arrived back in Australia late on Friday. Some Labor MPs are depressed and nervous about the saga, with some saying the government's best hope is for Mr Slipper to resign from the Speaker's role.

''We have fluid coming out of both of our ears,'' one MP said. ''It gets to the point where there is too much lead in the saddlebags.''

Another was critical of Ms Gillard's handling of the situation but was sympathetic to the argument it would be difficult for her to insist Mr Slipper remain out of the Speaker's chair until after claims of sexual harassment - separate to the criminal allegations of misuse of travel entitlements - are heard in court.

''Wouldn't that just encourage people to make claims?'' the MP said.

The Greens MP Adam Bandt said Mr Slipper should not return to the chair until the Cabcharge affair was ''clarified''. But the Minister for Trade, Craig Emerson, defended Mr Slipper saying it was unfair to criticise him for vague trip descriptions on the dockets. ''If there's a new standard which says that if Cabcharge has 'suburbs to city', 'city to airport', then that is a fraud against the Commonwealth, then just about every MP is guilty of a fraud against the Commonwealth,'' Dr Emerson said.

He also accused Tony Abbott of using ''weasel'' words to describe what the Coalition knew of the sexual harassment allegations. He said Mr Abbott's use of the word ''specific'' to deny any knowledge of the claims was ''weasel'' speak. ''What did Mr Abbott really know?'' he asked.

Opposition frontbencher Eric Abetz said the situation with Mr Slipper was like ''one big rats' nest''.