The industrial watchdog began an inquiry into the Health Services Union in April 2009, which became a fully-fledged investigation in March 2010.

Part of the investigation is inquiring into claims a credit card authorised by Mr Thomson, the former HSU national secretary and now member for the New South Wales seat of Dobell, was used for cash withdrawals, lavish meals and prostitutes. Mr Thomson has denied the allegations.

Fairfax has reported the investigation's findings against Mr Thomson, the union's president Michael Williamson and national secretary Kathy Jackson, are adverse.

Fair Work's general manager Bernadette O'Neill said in a statement yesterday that the investigation was ``nearing conclusion''.

She said that 6500 pages of documents had been sent to those against whom findings had been made.

``Varying deadlines to respond were given depending on the volume of material,'' she said. ``Three persons have been granted limited extensions.''

The final response was due on March 5.

Ms O'Neill said she would then consider whether the matter should go to the Federal Court for civil proceedings or be referred to the Director of Public Prosecutions as a possible criminal matter.

Prime Minister Julia Gillard said yesterday that she had no knowledge of the investigation's findings.

``Anything about the investigations . . . I only know from today's newspapers,'' she said.

``They are independent of us. The investigation is in progress and it should conclude.''

Opposition Leader Tony Abbott said the length of time it had taken to investigate the matter was ``scandalous'' and the report should be released.

``In the light of today's reports I call on the Prime Minister to stand up . . . and declare whether or not she still has full confidence in Craig Thomson.''