Federal Labor and the Greens say the Government has botched the handling of its centrepiece industrial relations bill, which will be introduced when Parliament returns today but is not guaranteed to pass.

Key points: Government pushes for reinstatement of ABCC

The Coalition yesterday executed a swift about-face and agreed to show a representative from both parties a secret volume of the trade union royal commission report.

The Government is using the royal commission to push for the reinstatement of the construction industry watchdog, the Australian Building and Construction Commission (ABCC).

Workplace Relations Minister Michaelia Cash earlier on Monday said showing the parties the confidential volume was pointless because they already opposed the ABCC.

But on Monday night Senator Cash said Labor and the Greens could join crossbench senators in viewing a redacted version, which would remove the names of witnesses and features which could identify them.

"This is all about getting good policy through the Senate," she said.

"And on that basis we have determined that we will give access to the confidential volumes to one member of the Australian Labor Party and one member of the Australian Greens."

A spokesman for Labor's workplace relations, Brendan O'Connor, accused the Coalition of playing politics.

"The Government has got itself into a mess," she said.

"It's either confidential or it's not. The Liberals are clearly engaged in the most base of transactional politics."

Greens industrial relations spokesman Adam Bandt labelled the situation farcical.

"The bells haven't even rung to start the first day of Parliament and already the Government's just making decisions on the run," Mr Bandt said.

"This handling of this supposedly flagship bill of theirs is just descending into farce."

Strict rules would apply to those viewing the documents, including a ban discussing the findings with anyone else, including fellow parliamentarians, with fines or jail terms as potential penalties.

The documents must also be viewed in the presence of an officer from the Department of Prime Minister and Cabinet, and notes and photographs cannot be taken.

"Everyone who is being asked to vote on this legislation — which we're being told is necessary because of the material in this secret report — should be entitled to see the report," Mr Bandt said.

"There should be one class of senators and not two."

Illegal behaviour not confined to construction: Madigan

Industry Minister Christopher Pyne will introduce the legislation into the lower house on Tuesday afternoon.

The Government's bid to reinstate the ABCC was blocked by the Senate last year and its success this time is far from assured, with only two crossbenchers contacted by the ABC on Monday pledging their support.

South Australian Family First senator Bob Day and Liberal Democratic senator David Leyonhjelm will vote for the law, which needs six of eight crossbench votes to pass.

Senators Nick Xenophon, John Madigan, Dio Wang, Jacqui Lambie, Ricky Muir and Glenn Lazarus were undecided or undeclared.

Palmer United Party senator Dio Wang said he wanted to move amendments broadening the ABCC to a national corruption watchdog.

"It's probably a very good opportunity for all parliamentarians to talk about whether we need a national corruption watchdog rather than have legislation to deal with building and construction industry on its own," he said.

Independent Victorian senator John Madigan said he was unhappy all politicians could not access the secret volume, and said illegal behaviour was not confined to the union movement.

"Why aren't they prosecuting this illegal behaviour now? The question is whether more laws will deliver more prosecutions," he said.

"I'm extremely uncomfortable with how the Government's been playing this issue, that [it] is offering [to show the confidential volume] to crossbench senators who request it but not sharing it with the entire Parliament."

Misconduct within the Construction, Forestry, Mining and Energy Union (CFMEU) was a key finding of the Heydon royal commission.

Senator Cash said multiple reports, including the Heydon royal commission, proved the need for the ABCC.

"The building and construction industry has been found to have proven itself to be unique in terms of a failure to comply with workplace laws," she said.

"So, this regulator ensures those who participate in this industry comply with workplace laws; nothing more and nothing less."