More than 200 workplace awards will be reviewed in the biggest overhaul to the State's industrial relations system in a decade, potentially boosting or reducing pay for more than 100,000 workers.
A Bill to be introduced in Parliament today seeks to align the State's IR system closer to the Federal one, partly by modernising all private- sector awards.
The 12-month review will decide whether to increase or decrease such things as basic wages, overtime rates, allowances and apprentice pay.
Commerce Minister Simon O'Brien refused to guarantee that workers would not take home less pay as a result of the review, but said this was not the Government's intention.
A similar Federal review reduced pay for some workers, though they were eligible to apply to have wages preserved through the Federal industrial umpire, Fair Work Australia.
In most cases, pay cuts in one area - such as overtime - were offset by a pay rise in another area.
The changes could affect anyone in WA's private award system, including retail, hospitality and transport workers employed by unincorporated bodies, sole traders and partnerships.
There are nearly 500,000 workers in the State system, though most are in the public sector, which is not part of the review.
The Bill, which will be open to consultation until late January, is likely to anger unions on several fronts.
It will seek to restrict access to unfair dismissal laws after a year for small businesses with fewer than 15 employees. Currently there is no time restriction.
It will introduce a fit and proper person test for right-of-entry permits, which could deny permits to those with industrial or criminal records.
For the first time, unions would be required to give 24 hours notice before entering a site.
Immediate access would be granted for safety matters, but unions would have 24 hours to provide a valid reason for seeking urgent access.
The proposed changes have wins for workers with new minimum conditions of employment, including two days of paid compassionate leave in some circumstances.
Another minimum condition would ensure workers who took annual leave when there was a public holiday would get that time off later.