But Dr Napthine's stand has been undermined by revelations that the performance of the deputy leader, Louise Asher, is under review, with senior colleagues warning she could be dumped from the treasury shadow portfolio by the end of the year.

Senior Liberals also revealed that shadow attorney-general Robert Dean came under attack during the recent party room meeting, with some MPs accusing him of pre-empting the party's position on Labor's Relationships Bill.

The developments follow criticism by Liberal frontbenchers of tactics adopted by Dr Napthine, Ms Asher, the party's upper house leader, Mark Birrell, and his deputy, Bill Forwood.

Several frontbenchers privately accused the leadership group of failing to capitalise on the government's perceived weaknesses; of being too cautious; and allowing voters to think the Liberals do not stand for anything.

Dr Napthine said the Liberals would use their upper house majority to defeat Labor's Fair Employment Bill, claiming the proposals would cost 40,000 jobs and be against the interests of small business.

He said the bill was unnecessary as the Howard Government had recently moved to protect low-paid workers by amending the federal Workplace Relations Act.

The State Government and Trades Hall Council has attacked the decision.

Dr Napthine said the Liberals would seek to block the Relationships Bill unless Labor withdrew the proposals.

"It has absolutely horrific untoward consequences for people in long-term relationships, for families and it should be absolutely redrafted from scratch," Dr Napthine said.

Premier Steve Bracks accused the opposition of blocking the government's reform agenda because it was bereft of policy.