Labor to keep union royal commissioner Heydon in sights

Federal Labor has vowed to continue a pursuit of the government over its hand-picked royal commissioner for the trade union corruption inquiry, when parliament sits on Monday.

Former High Court judge Dyson Heydon was billed to deliver the 2015 Sir Garfield Barwick address later in August, but pulled out last week after being told it was an event organised by the Liberal Party.

But Labor workplace relations spokesman Brendan O'Connor insists there is a conflict of interest that taints the royal commission "from beginning to end".

He believes there are also questions over the conduct of the commission more broadly.

But Attorney-General George Brandis has called Labor's attempted smear campaign of Mr Heydon a disgrace and has described the conduct of the former judge as "unimpeachable".

Mr O'Connor has demanded that Prime Minister Tony Abbott reveal how much Mr Heydon is being paid.

In a letter to Mr Abbott on Sunday, he said the public had a right to know the taxpayer-funded salary of Mr Heydon.

Mr O'Connor said the opposition had "serious concerns" about the government's failure to publicly account for Mr Heydon's salary and accused the government of frustrating public scrutiny by claiming the matter was "commercial in confidence".