The final report of the investigation into Labor MP Craig Thomson and the Health Services Union he headed may be kept under wraps.
Since 2009 Fair Work Australia (FWA) has been examining allegations of financial irregularities at the union formerly headed by Mr Thomson, now the MP for the NSW seat of Dobell.
It's been claimed Mr Thomson used union credit cards for prostitutes, lavish meals and cash withdrawals - claims he denies.
The backbencher's vote is crucial to the survival of the Gillard minority government.
FWA has concluded its investigation but has asked for Mr Thomson and two other union officials, Kathy Jackson and Michael Williamson, to comment on a list of 'possible contraventions' by March 5 before finalising its action.
That could include civil action under industrial laws or a referral to prosecutors for possible criminal action.
The opposition has called for the investigation to be wrapped up immediately and all details publicly revealed.
However, a spokesman for FWA told AAP on Friday, 'No decision has been made on whether the investigation report to be provided to the general manager (of FWA) will be made public.'
The spokesman said the investigation would be 'concluded as soon as practicable after taking into consideration any responses provided'.
Opposition frontbencher Christopher Pyne said Prime Minister Julia Gillard should insist FWA publicly release its report.
'It's now taking upwards of three and a half years for the Fair Work Australia inquiry to be completed ... and in anybody's language that is far too long,' Mr Pyne said.
He said Ms Gillard also needed to tell parliament next week whether she had full confidence in Mr Thomson.
