PM must take responsibility for HSU:Abbott

The opposition says the PM is still relying on

The opposition says the PM is still relying on "the tainted vote" of ex-HSU official Craig Thomson. (AAP)

Opposition Leader Tony Abbott says the prime minister is still relying on "the tainted vote" of ex-HSU official Craig Thomson in parliament.

The arrest of the former health union boss Michael Williamson has prompted opposition calls for the prime minister to stop relying on the vote of fellow ex-HSU official, independent MP Craig Thomson.

Opposition Leader Tony Abbott said Australians would be shocked Mr Williamson had been arrested in Sydney and was facing possible criminal charges.

Police say Mr Williamson will be charged later on Thursday over his alleged involvement in the Health Services Union scandal.

Mr Williamson, who walked into Maroubra police station in Sydney's east on Thursday morning, is a former national president of the HSU while Mr Thomson was its national secretary before he was as a federal Labor MP in 2007.

"Plainly the prime minister has got to take responsibility for this," Mr Abbott told reporters in Melbourne on Thursday.

Ms Gillard was the last person in the country to express full confidence in Mr Thomson, he said.

"The prime minister is still relying on the tainted vote of the Health Services Union representative in the federal parliament."

Mr Abbott said until Ms Gillard completely repudiated the type of union activity alleged at the HSU, the public would conclude the government was "seriously ethically challenged" and that "...this is a prime minister who lacks judgement as well as lacking competence."

Mr Thomson, who is suspended from the Labor party, denies Fair Work Australia findings he used union credit cards to pay for lavish meals, accommodation and prostitutes.

Ms Gillard would not be drawn on the matter.

"I'm not going to comment on a police matter," she told reporters in Hobart.

"I don't want to be speaking about a matter which will ultimately be dealt with by the courts."