Unions say the decision by Western Australia's Industrial Relations Commission to award workers on the minimum wage a $13-per-week pay rise will lead to growing numbers of working poor.

The commission handed down its decision in the annual State Wage Case, which affects up to 200,000 low-paid workers covered by the WA industrial relations system.

From July 1, the minimum wage will rise from $679.90 per week to $692.90 per week, representing an increase of 1.9 per cent.

Unions WA had sought a $30-per-week rise, while the Chamber of Commerce and Industry had argued for a wage freeze.

In its submission to the commission, the State Government said an $8.50-per-week increase was appropriate in the current economic climate.

Unions WA secretary Meredith Hammat said the increase would do little to help struggling workers.

"We are deeply disappointed by this decision and certainly those on the minimum wage in WA will find that this increase is not enough to compensate them for the high costs of living in WA, particularly in Perth," Ms Hammat said.

"It's a decision that's less than the outcome in the national wage case decision and it's a decision that is less than the increases workers are experiencing in rent, in health, in education and in other essential costs of living.

"We don't want to go down the American path where we have working poor, people in full-time jobs but unable to afford the essential costs of living for themselves and their families."

In a statement, Commerce Minister Michael Mischin said the needs of the low paid should be considered without adversely affecting the viability and competitiveness of the businesses that provided their jobs, in particular small businesses.

"It is important to acknowledge the value and contribution that all workers make to the Western Australian economy, and to make sure that the real wages of the lowest paid and most vulnerable are protected," Mr Mischin said.

He said the WA Government's submission to the State Wage Case had sought an adjustment to maintain the real wages of employees on the minimum wage or award rates of pay.

Peak business body says WA's labour costs among the highest

The Fair Work Commission recently lifted the national minimum wage by 2.4 per cent to $672.70 per week.

The Chamber of Commerce and Industry of Western Australia (CCI) said the decision would increase pressure on small businesses and act as a further barrier to employment.

Chief executive Deidre Willmott said the $13-per-week increase was above the predicted level of inflation and would mean less working hours for part-time and casual workers.

"Most small business owners will not be able to pass this increase in costs onto consumers, so owners will likely work more hours in the business themselves, taking shifts away from part-time and casual workers and inhibiting job creation," Ms Willmott said.

"While today's decision will reduce the gap between the state and national minimum wages somewhat, WA's small sole traders and partnerships in WA will still be paying a $20 per week more than businesses covered by the national industrial relations system."

She said WA's small businesses continued to be penalised with higher labour costs than other states.