Tony Abbott will divert some of the funding from the royal commission into trade union corruption to set up a joint police taskforce into “corrupt behaviour, unlawful kickbacks and standover tactics” in Victoria.

The prime minister joined the premier, Denis Napthine, in Melbourne on Friday to announce the federal and Victorian police unit focusing on criminal conduct by unions and their associates – four weeks before the state election.

The Liberals in Victoria have previously targeted the state opposition leader, Daniel Andrews, over his links to the CFMEU.

Napthine called on Andrews “to not only support this police task force but to instruct the CFMEU and ACTU leadership to fully cooperate with this task force”.

Asked whether the announcement was an attempt to wedge Andrews in the lead-up to the election, Abbott said he expected the taskforce to gain bipartisan support given the federal opposition leader, Bill Shorten, had previously called for the move.

“I don’t think any decent person wants to see union corruption and criminality continuing,” Abbott said. “I don’t think any decent person wants to see unions contaminated by organised crime.”

About 30 officers, mostly from the Australian federal police (AFP), will form the taskforce. Similar joint units are likely to be set up in other states.

“The taskforce will be funded by the commonwealth out of the royal commission budget,” Abbott said. “We believe that the $50-odd million we’ve allocated to the royal commission will cover this taskforce and any other taskforce that will be established.”

In February, as the federal government prepared to launch the royal commission, Shorten called instead for Abbott to set up “a high-powered joint police taskforce to immediately investigate allegations of corruption reported in the building construction industry”.

Shorten said at the time that a royal commission would be a politically motivated “stunt” which would not have the power to arrest, charge or prosecute.

“Under the opposition’s proposal, a multi-jurisdictional taskforce would be led by the Australian federal police and include state police forces, to investigate allegations of corruption in the building construction industry, including union representatives and employers,” Shorten said on 9 February.

The government recently extended the royal commission’s terms of reference and reporting deadline.

Abbott said the royal commissioner, Dyson Heydon, had found evidence of criminal conduct, including physical and verbal violence, cartel conduct, secondary boycotts, contempt of court and the encouragement of others to commit these contempts.

“It’s very important under these circumstances that this kind of criminal activity be fully investigated and tackled by the people who are best placed to deal with this – and obviously that’s the police,” Abbott said on Friday.

The assistant secretary of the ACTU, Tim Lyons, said the allegations should have been referred to police in the first place.

Shorten said Abbott’s announcement was “more to do with Victorian electoral politics”.

“What the prime minister has announced today is exactly what I announced nine months ago,” Shorten said.

“They say that imitation is the best form of flattery. This copycat prime minister has to explain why he has waited nine months to make this announcement.”