The move came as the Australian Federal Police confirmed it had begun a criminal investigation into further allegations by James Hunter Ashby that Mr Slipper misused publicly funded cab vouchers.

Mr Pyne had initially said his contact with Mr Ashby had been brief, but it was reported the senior MP had spent almost two hours drinking and chatting with Mr Ashby in the Speaker's office a month before Mr Ashby lodged documents in the Federal Court in Sydney.

Mr Pyne clarified he had met Mr Ashby three times - twice in the Speaker's office and once when the staffer came by the Liberal MP's office.

Initially saying he had never requested Mr Ashby's phone number, Mr Pyne yesterday clarified that he had sought the number but had never spoken with Mr Ashby on the phone.

Both Mr Pyne, who has regular contact with the Speaker's office as manager of opposition business in the lower house, and Opposition Leader Tony Abbott have said they had no ``specific knowledge'' of the pending court action.

Mr Abbott yesterday walked away from reporters in Sydney when a question was raised about the matter.

Labor frontbencher Craig Emerson said the use of the phrase ``specific knowledge'' by both Mr Pyne and Mr Abbott pointed to a cover-up.

``Mr Pyne does need to stand up . . . and explain why he seeks to evade and to conceal the true involvement of the Liberal Party in the preparation of this document by Mr Ashby,'' Dr Emerson said.

``There are very large missing parts to this story and the Australian people deserve to know the missing parts of the story.''

Mr Pyne said he first found out about the court action in newspapers.