Heather Ridout, the chief executive of the Australian Industry Group, has said in a submission to a Senate inquiry that the laws were being introduced in an economic environment that was already "immensely tough and challenging".

In addition, business faced increased costs from the Rudd Government's emissions trading scheme, which is to begin in 2010, as well as superannuation changes introduced last year. If unions exploited the concessions granted to them under the Fair Work Bill, they would threaten workplace harmony and jobs.

"In the current environment, excessive improvements in working conditions and the reckless use of the proposed increase in union power will be at the expense of jobs. Jobs are the priority, together with protecting industry from workplace relations turmoil," Ms Ridout said.

Ms Ridout was a member of the business advisory group on workplace relations that advised the Government on the make-up of its legislation which will replace the Howard government's Work Choices.

While unions think the laws are still unfair, Ms Ridout cited specific areas of concern.

These included the increased right of entry for unions which, she said, should be abolished along with provisions that allow the compulsory arbitration of disputes involving the lowest-paid workers.

The Treasurer, Wayne Swan, said the criticism from unions and business showed the package to be balanced.