Builders warn a new super-union featuring the CFMEU and dock workers will have the power to hold Australia's supply chains to ransom.

But the newly-christened CFMMEU – with the extra ‘M’ – says it will fight for workers to get pay rises and corporations to pay tax.

The Construction Forestry Mining and Energy Union (CFMEU), the Textile Clothing and Footwear Union of Australia (TCFUA), and the Maritime Union of Australia (MUA) will become one union after the Fair Work Commission approved their amalgamation.

The super-union will become the CFMMEU, with “Maritime” added to the name from March 27.

“It’s time for big business to stop riding on the coat-tails of everyday working Australians, time the banks stopped ripping people off, and time for every business in this country to pay tax,” CFMEU secretary Michael O’Connor, who will also be secretary of the new organisation, said on Tuesday.

But the Master Builders Association, who tried to stop the merger in the Fair Work Commission, says the new organisation will have the capacity to shut down multiple supply chains.

“It is hard to imagine any other situation where a merger with ramifications so dire would be allowed to happen,” chief executive Denita Wawn said.

“The key partners in this ‘super-union’ seem to take pride in taking illegal action, believing they are above the law which applies to the rest of the community.”

Former MUA boss Paddy Crumlin, the international president of the new union, said it represented a renewal of the movement.

“Wherever there is a need to defend the interests of Australian workers, we will be there with them in their workplaces and communities,” he said.

The federal government in 2017 warned the merger would create “industrial chaos”, but legislation it introduced trying to apply a public interest test to mergers didn’t get past the Senate.

Workplace Minister Craig Laundy said it was not unreasonable to ask if unions who regularly break the law and aren’t deterred by fines should come together.

“There are limited grounds for the government to intervene in these matters, even when the merger can have a major economic impact,” he said.

By Angus Livingston