Building probe not about Vic poll: Brandis

The formation of a task force to investigate union corruption in Victoria has nothing to do with the upcoming state election, federal Attorney-General George Brandis says.

Prime Minister Tony Abbott and Victorian Premier Denis Napthine announced the joint federal-state police task force on Friday, saying it would crack down on corruption, violence and organised crime connections in the construction industry.

The investigation had been prompted by evidence given to the Heydon Royal Commission into the unions, the two leaders said.

But critics in the Labor Party and union movement have questioned the timing of the task force.

Senator Brandis denied it had been announced ahead of the November 29 state poll to help with the re-election of the Napthine Liberal government.

"It's got absolutely nothing to do with it - the royal commissioner (Dyson Heydon) has absolutely nothing to do with the political events of the day," he told the Ten Network on Sunday.

"A royal commissioner is entirely independent of government."