Police have received a claim that Senator Bill Heffernan assaulted an employee of Chris Hartcher, the NSW Energy Minister, in an alleged homophobic attack at a Liberal Party meeting on the state's central coast.

Ray Carter, 67, has accused Senator Heffernan of striking him so hard he was knocked off balance.

He claims Senator Heffernan later approached him and said, ''I didn't know you were a poofter.''

The row comes as Labor braces for more controversy as its suspended MP, Craig Thomson, explains to Parliament how he spent almost half a million dollars of union funds during his time as national secretary of the Health Services Union.

Mr Abbott has demanded Prime Minister Julia Gillard refuse to accept the ''tainted vote'' of Mr Thomson, despite the MP facing no charges and being suspended from the Labor caucus and moving to sit with the independents.

Trade Minister Craig Emerson said yesterday Senator Heffernan was entitled to due process and the presumption of innocence.

''If Mr Abbott applied his own principles he'd refuse to accept Senator Heffernan's tainted vote, he will stand him down from chairing the relevant Senate committee and he will move to dismiss Senator Heffernan from the Liberal Party,'' he said.

Mr Abbott has consistently called on Mr Thomson to make a statement to the Parliament.

Dr Emerson said it would follow that under Mr Abbott's principles, Senator Heffernan should be forced to explain himself too.

''Mr Abbott can't have it both ways … consistency is what we seek,'' he said.

Workplace Relations Minister Bill Shorten also portrayed the alleged incident as a test for Mr Abbott.

''I think the challenge here is, will he rush to judgement again when it's his own party or will he take the more measured Labor approach of saying that you have to go through a process,'' he said.

Later, Mr Abbott rejected Labor's demands to act against Senator Heffernan.

''There is simply no parallel between the official Fair Work Australia investigation findings against Craig Thomson and this allegation against a Liberal senator,'' his spokesman said last night.

''Whilst the government has disowned Craig Thomson from the caucus, they still cling to his vote in the Parliament.''

Mr Carter is currently suspended from his job while he is investigated for allegedly accepting donations from a property developer.

It is understood Senator Heffernan had made the report against Mr Carter.

Former prime minister John Howard forced Senator Heffernan to apologise after falsely claiming in Parliament that Justice Michael Kirby used Commonwealth cars to procure young men for sex.

NSW Liberal president Senator Arthur Sinodinos, who was at the May 3 meeting, said neither he nor state director Mark Needham witnessed ''any incident, assault or even minor disturbance''.

''None of the attendees raised any complaints or reported any incidents to either the president or director at the conclusion of the meeting,'' he said.

Senator Sinodinos said the party had reviewed statements from Mr Carter and two other witnesses and said it did believe there was any substance to the allegations.

The industrial watchdog, Fair Work Australia, concluded after a three-year inquiry that Mr Thomson misused union funds, including on electioneering, dinners and prostitutes.

The sum included almost $300,000 on his election campaign for the federal seat of Dobell. The Australian Electoral Commission says Mr Thomson declared that money in accordance with the Electoral Act.

Mr Thomson denies the allegations and says he was set up by a rival to destroy his political ambitions.

He has hinted he will name the person today under parliamentary privilege and may suggest he was a victim of identity fraud.

He is tipped to accuse Kathy Jackson, who succeeded him at the union, of destroying documents that would have cleared him of charges that he spent thousands of dollars of union funds on personal expenses.

Ms Jackson denies the allegations.

The Opposition says it will be wary of any bid by Mr Thomson to table documents in his defence, saying it is unclear whether tabling could preclude their use in any legal action.