UPDATED 7.36PM: National's scrambling to present a united front after backbencher Judith Collins was rumoured to have stalled workplace health and safety changes.

A select committee is two months late reporting back on legislation drafted after the Pike River disaster - division within National is rumoured to be the cause.

Collins said today reports she's led the caucus opposition to the Bill are incorrect, but she did say it needs changing.

"Most people just want to make sure that when we do put this law through, that it actually ends up with some really good outcomes for workers, and that it doesn't actually just create bureaucracy that gets ignored," she said.

"We want it to work and work well."

Senior MP Anne Tolley wouldn't directly answer questions about the matter, aside from admitting the party has had "robust" discussion.

"At the end of the day we all work together, we're all very focussed on making sure we have safe workplaces but we also want to make sure we don't make it too onerous for businesses."

The Prime Minister expressed his confidence in both Collins and Maurice Williamson, who had made overtures of joining the ACT Party, but didn't give them ringing endorsements. 

"Maurice is Maurice," Key said. "He's there and he's doing his job."

When asked if Collins would ever regain a Cabinet posting Key said "Maybe one day, but there'd have to be an opening for that."

Judith Collins resigned as Justice Minister before last year's election as pressure built about accusations she had conspired with blogger Cameron Slater to undermine and attack a public sector chief executive.