Mr Thomson already faces allegations, revealed by the Herald, that his card was used to pay for escort services in Sydney, and to make more than $100,000 in cash withdrawals.

Mr Thomson has denied the allegation of irregular spending - still the subject of an investigation by Fair Work Australia.

He claims he authorised payments but other people had access to the card. This new information appears to call that position into question.

Bills and credit card details obtained by the Herald reveal that:

On April 5, 2006 a call was made from Mr Thomson's hotel room at the Grand Hyatt in Melbourne to Young Blondes escort agency and later to Confidential Models escort agency.

On June 7, 2006 a call was made from his room at Pacific International Suites in Melbourne to an escort agency called Bad Girls.

Another bill shows that on May 15 of that year, Mr Thomson spent $805.50 on lunch at the Melbourne restaurant Langton's. It appears only $102 was on food - $540 was for four bottles of wine and the rest on beer and coffee.

Mr Thomson declined to comment on the invoices last night.

With the federal government again under pressure to defend Mr Thomson, the Herald has learnt that Fair Work Australia paid $7092 for legal advice to shut down questioning by the opposition about the investigation into the Health Services Union's financial reporting.

During a budget estimates hearing in February, the Liberal senator Michael Ronaldson questioned Terry Nassios, the Fair Work Australia officer charged with investigating the allegations. He asked Mr Nassios who had been interviewed, and if Mr Thomson had been interviewed.

At an earlier hearing, Mr Nassios said answers to those questions could damage his investigation, but this time he said he believed the answers could be safely made public.

But as he prepared to answer, he was interrupted by the Labor Senate leader, Chris Evans, who said: ''I would like to get some advice before the officer made available details as to who has been interviewed.''

The line of questioning was ended and Senator Ronaldson has since learnt that Fair Work Australia took advice from Peter Hanks, QC, who charged $7092 to advise that revealing who had been interviewed would not be in the public interest.

Senator Ronaldson had planned to ask if Mr Thomson had been interviewed and what Fair Work had discovered.

Senator Ronaldson said yesterday that it ''beggars belief'' that a senator would ''shut down'' a bureaucrat who had decided to make information public. ''They will do and say and spend anything to prevent the inevitable - Thomson going down and a fresh election being held,'' he said.

This week it was reported that the Labor Party had spent up to $90,000 on Mr Thomson's legal fees from a withdrawn defamation action against the Herald, saving Mr Thomson from bankruptcy and disqualification from office.

It was revealed in earlier estimates hearings that as of February 2010 the inquiry cost $162,908.10, not including the time of the two staff members.

Senator Evans's office did not respond to calls.

Should the Fair Work investigation reveal wrongdoing, it could apply to the Federal Court to have a civil penalty applied or refer the matter to the Director of Public Prosecutions.

Mr Thomson has not been charged with anything and on Sunday, Wyong police said they were not investigating a complaint lodged by a member of the Health Services Union.

Sources close to the MP were blaming the former Labor powerbrokers Graham Richardson and John Della Bosca for stirring up fresh allegations.

In Parliament yesterday the Prime Minister, Julia Gillard, was again questioned over Mr Thomson and again said she stood by him. She declined to say when she became aware that the Labor Party had lent him money for legal bills.

The Opposition Leader, Tony Abbott, accused Ms Gillard of protecting Mr Thomson to save her government but he would not agree that she should call for Mr Thomson's resignation. A Liberal senator, Mary Jo Fisher, is awaiting trial after being charged with shoplifting.

''I don't want to … set myself up as a moral paragon because you never know what tests you might face,'' Mr Abbott said.

If Mr Thomson were forced to resign, the government would probably lose its parliamentary majority at a byelection.