John Howard has criticised the Turnbull government for failing to legislate a "public interest test" for union mergers before the construction and maritime unions combined.
The former prime minister wants the coalition to revive its plans as mining groups appeal the merger of the Construction Forestry Mining and Energy Union, Textile Clothing and Footwear Union of Australia and the Maritime Union of Australia.
"I am very disappointed that the public-interest-test legislation has not gone through the parliament and I would hope the government would re-present that," Mr Howard told The Australian on Friday.
Labor frontbencher Anthony Albanese said it was up to union members to determine mergers.
"This is anti-union rhetoric from an anti-union government based upon ideology," Mr Albanese told the Nine Network.
"It is up to the members of a trade union to determine what union they want to join."
Cabinet minister Mathias Cormann said the government remained "100 per cent" committed to convincing the Senate to support the public interest test bill.
"Any suggestion that somehow the government abandoned the reintroduction of the public interest test on union mergers is false," Senator Cormann told Sky News.
He said pushing ahead without the numbers would have taken up time for other legislation or sunk the merger test legislation, forcing the government to start from scratch.
"We continue to work to secure the necessary support. As soon as we do, we of course will press ahead," Senator Cormann said.