Australian Workers' Union national secretary Daniel Walton and CFMEU national president Tony Maher said in a joint statement that Queensland Premier Annastacia Palaszczuk had the power to act today.
They said the approval would save 150 existing full-time jobs and create an additional 700 positions.
"She should do so," they said.
"It is unacceptable for the state government to rely on the excuse that the matter is ‘before the courts.'."
Over the course of the 13 years since New Hope Corporation first began to seek approval of New Acland Stage 3 there have been four court hearings. New Hope have won three, and the fourth hearing was found to be infected by the apprehension of bias.
"It is possible to bog this project down in endless litigation," the unionists said.
"That is precisely what opponents of the expansion plan to do."
The unionists said that with the economic effects of COVID-19 playing havoc with the state's economy and the prospect of more job cuts at New Acland in the near future due to the delay of this project, the Queensland government could no longer just sit on the sidelines.
"The Queensland government has the power to approve the project and, for the good of the state, it must do so," they said.
"Premier Palaszczuk approved the Adani Carmichael project despite continuing legal action, so too should she approve Stage 3 of the New Acland Mine.
"New Acland Coal provides energy certainty to domestic customers that employ more than 14,000 Queenslanders. Expansion is projected to contribute $7 billion to the Queensland economy.
"We understand that there are noisy interests who are vehemently opposed to the project going ahead. But their desires should not be prioritised over the livelihoods of blue-collar workers in regional Queensland, the energy security of customers, and the health of the state's economy -particularly during this time of crisis."
The unionists said the Queensland government said it was seeking shovel-ready projects to stimulate the economy at this time.
"There is no project more shovel-ready than Stage 3 of the New Acland mine," they said.