The New South Wales branch of the CFMEU's construction division has posted a defiant video to social media, praising the union's leadership and declaring the organisation is under an "unprecedented attack".

It follows the decision of the federal and state Labor parties to sever ties with the union's construction division over corruption allegations.

The video, posted to Instagram, shows dozens of union members standing in what appears to be a meeting room at the CFMEU's head office.

"External forces attacking the CFMEU have one agenda only: to reduce your collective power through the Union to win better wages and conditions," the video's caption said.

"The governments, state and federal, the big end of town, and the ACTU want you to work for less and in unsafe conditions.

In the video itself, members thank the CFMEU leadership in NSW.

"We want to say thank you to our executives in our head office here," one speaker said.

"We want to say thanks to them for always being at the cornerstone of safety on site, making sure our work rights are well intact and improved, making sure our wages are going up with inflation so we can provide for our families and live decently," one union member told the camera.

The State Secretary Darren Greenfield and his son Michael are among the executives singled out for praise, while making no mention of the corruption charges both of them are facing.

Despite being charged in 2021, neither have been convicted and they remain at the helm with the support of members, having denied the allegations.

The video ends with members repeatedly chanting "union power".

'They are innocent', construction president says

After more front-page allegations were published in the Nine newspapers on Tuesday, both the premier and prime minister said they would push to have an independent administrator appointed to run the union's construction division.

However, NSW president of the CFMEU's construction division, Rita Mallia, said the union would oppose that move and "defend the union's position".

"It's an unjustified, knee-jerk reaction to untested and baseless allegations coming out of a media story."

Ms Mallia refused to speak about the specifics of the allegations levelled at both Darren and Michael Greenfield, but said the rank-and-file members supported them.

"We have every confidence that our current leaders in New South Wales will be vindicated and that they are innocent of these matters.

"They'll get their day in court and they ought to be given that opportunity, like every other person in New South Wales, to do so."

She said the Instagram video was the beginning of a campaign against what she said was an "attack."

"That video is but a snippet of the feeling, the genuine feeling that's felt by the members towards the union [and] their anger against both the state and federal government.

She said the CFMEU wouldn't be "distracted by politics".

"We'll continue in whatever form that we're able to, to continue to fight for our members and ensure that they get home safely every night, and that they can pay their bills and put something away for the future.

"We don't play politics. And if the ALP chooses to do so, well, that's their choice."

'Don't fight', Minns warns CFMEU

Having previously called for Mr Greenfield's resignation, Premier Chris Minns on Tuesday asked the Labor Party to sever ties with the union and reject further donations and affiliation fees.

He also backed the Albanese government's plan to appoint an independent administrator to the CFMEU, vowing to support the move in the NSW Industrial Relations Commission.

On Wednesday he warned the CFMEU not to fight the action.

"We want to make it clear that we're not resigning from that decision," Mr Minns said.

"We'll take any steps that are deemed necessary to put in an independent administrator on the basis that that union has proven unwilling or unable to reform themselves.

"If we can't do that through the industrial relations legislation in New South Wales, we will pursue legislation."

However, he again rejected opposition calls for Labor to repay the donations and affiliation fees it's previously accepted from the union.

"[They've] been spent. It's not like they're sitting in a bank account waiting to be returned," he said.

Acting Opposition Leader Damien Tudehope has called for Labor MPs to be levied to recover the equivalent amount, with that sum donated to charity.

However, the premier said the Liberal Party was setting a standard it may come to regret.

"I expect him to abide by that standard in the weeks, months and years ahead," he said.

"If there's allegations about tainted donations through the ICAC or through other forums, clearly Mr Tudehope has this indicated that the Liberal party would raise that money from their MPs and donate it to charity."

Ms Mallia said the union's construction division wasn't bothered by Labor's decision to sever ties.

"We don't really have a lot of respect for a party that does not have any respect for procedural fairness," she told ABC News.

"[Labor] shows no respect to its rank and file members who are members of the CFMEU.