TRADE Union Royal Commissioner Dyson Heydon failed to release information regarding his acceptance of an invitation to a Liberal Party event, union lawyers have claimed.
Union lawyers yesterday applied for Mr Heydon to remove himself from the commission due to the perception of bias.
The allegation follows revelations Mr Heydon was to speak at a Liberal Party function - despite unions and the Labor Party maintaining the royal commission is politically motivated.
Australian Council of Trade Unions lawyer Robert Newlinds stressed he was not accusing Mr Heydon of being biased, but rather that an independent observer may see potential biases.
Mr Heydon has claimed he was unaware the Sir Garfield Barwick speech he agreed to give was in fact a Liberal fundraiser, but CFMEU lawyer John Agius yesterday alleged some documents regarding Mr Heydon's acceptance had not been released.
After initially claiming an impartial observer may believe the documents had been "doctored" so an attachment for "state donation compliance" did not appear, Mr Agius later said it was possible they had "dropped off" an email chain.
Australian Workers Union lawyer Herman Borenstein said Mr Heydon's ignorance of the speech being a party fundraiser was irrelevant to the perception of bias.
"Once the Commissioner has been seen to associate with the Liberal Party, that taints the work that the Commissioner does in relation to this Commission," he told the commission.
Mr Heydon is expected to make a ruling on his own potential bias on Tuesday.