In a statement issued this afternoon Fair Work Australia general manager Bernadette O’Neill said an investigation into the HSU national office revealed an organisation “that abjectly failed to have adequate governance arrangements in place to protect union members’ funds against misuse”.

“Substantial funds were, in my view, spent inappropriately including on escort services, spousal travel, and excessive travel and hospitality expenditure,” Ms O’Neill said in the statement.

Ms O’Neill said the great majority of contraventions related to the former official.

Fair Work Australia spent years investigating the finances of the HSU’s national office, as well as allegations that federal Labor MP Craig Thomson misused a credit card when he was the national secretary of the union between 2002 and 2007

Mr Thomson has consistently denied the allegations and this afternoon maintained his innocence.

“Any proceedings brought against me in respect of the findings in the report will be strenuously defended,” he said in a statement.

“This whole investigation has been nothing short of a joke.

“It is unprecedented that an investigative body has such little confidence in its report that it seeks parliamentary privilege as a condition of the report’s release.”

Mr Thomson said the police had made it clear “there is nothing in the Fair Work Australia Report that is of a criminal nature”.

“The report is based on allegations – and that is all they are – have not been tested by a court.

“These assertions are not based on proper evidence.”

Mr Thomson said the FWA investigation indicated bias and a lack of fairness, and “was not properly conducted”.

Mr Thomson tweeted this afternoon: FWA gets it wrong again”.

Ms O’Neill said today she was unable to name the officials concerned “for reasons that include privacy obligations and the fact I have no protection against defamation”.

Fair Work’s 1100-page investigation report has been passed on to the Senate’s education, employment and workplace relations committee.

Ms O’Neill said she was now instructing solicitors “to initiate proceedings in the Federal Court of Australia”.

Ms O’Neill said an independent review of FWA’s investigations into the HSU national office and Victoria No.1 branch, which have been criticised for their slowness, would be completed by the end of July.

The review will cost around $430,000.