Opposition lawmakers have called on Prime Minister Julia Gillard to apply pressure on embattled Labor MP Craig Thomson to cooperate with all police inquiries that seek to shed light on the alleged corruption that marred the Health Services Union (HSU) operations under his watch.

Coalition frontbenchers Christopher Pyne and Scott Morrison were enraged that Thomson had begged off from talking with police investigators coming from the New South Wales despite his earlier decision to cooperate with the probe being conducted by the Victorian police on the matter.

According to the Australian Associated Press (AAP), Mr Thomson, who denied he paid for the services of prostitutes using HSU-issued credit cards and availed of cash advances, will not entertain any initiatives by NSW authorities to interview him pending an agreement with his lawyers.

"I declined on legal advice," AAP reported the Labor MP as saying on Monday.

The controversial legislator served as HSU's national secretary from 2002 to 2007 and is one of the subjects of the three-year probe conducted by the Fair Work Ombudsman, which has forwarded its findings to federal prosecutors.

His decision, Mr Thomson explained, was based on the fact that he was not in any manner involved with HSU's east branch after 2002, a period not covered by the FWA investigation.

Mr Thomson's declaration, according to Mr Pyne, would effectively sabotage the ongoing police investigation on the matter, which should prompt authorities to prosecute the Labor MP for obstructing the course of justice.

With the attitude being displayed by one member of the ruling Labor Party, Mr Pyne suggested that Ms Gillard should step in and put more pressure on Mr Thomson to reverse his position.

"She (Ms Gillard) needs to come out today and direct a member of her caucus to cooperate with the NSW Police in an investigation which is about the misuse of hundreds of thousands of dollars of members of the HSU's hard-earned money," Mr Pyne said in an interview ABC on Monday.

Also, Mr Morrison echoed the calls of his opposition colleague and stressed that Mr Thomson's stance was a disgrace for the Parliament.

"(Thomson) is a member of parliament. There should be no less a standard applied to him just simply because Julia Gillard's relying on his tainted vote for a tainted government," Mr Morrison said in an interview today with Network Ten.

"Julia Gillard must demand today that he cooperate with NSW Police immediately," the opposition frontbencher added.

The likely implication of Mr Thomson into criminal cases that could arise from the FWA probe may lead to his expulsion from the Parliament, according to legal experts, which in turn could trigger the early fall of the minority Gillard government.

Recent polls have been indicating that Ms Gillard and the Australian Labor Party will be easily beaten by the Liberals come the national elections in 2013.