The number of government departments in WA will be slashed from 41 to 25 under a suite of reforms announced by Premier Mark McGowan.

Key points: 40 per cent of government departments to be abolished or amalgamated

40 per cent of government departments to be abolished or amalgamated Number of job losses unclear

Number of job losses unclear Further public sector reform promised

Forty per cent of departments will be amalgamated or abolished under the plan, which is aimed at creating "a more efficient public sector to deliver better services for the community", the Premier said.

He said there would also be "a major reshuffle" of departmental chief executives, with 20 per cent of jobs in the 521-member Senior Executive Service - WA's highest paid bureaucrats - to go.

Prior to last month's election, Labor flagged that it would look for significant public sector savings in government in an attempt to ease WA's budget woes, promising a service priority review of government to gut $750 million from the public service over four years.

The number of job losses resulting from the reform is unclear.

"I have always had the view ... that there were too many government departments, too many government agencies across Western Australia which lead to duplication, a silo culture, a lack of collaboration between agencies that affected service delivery and job creation in Western Australia," Mr McGowan said.

Opposition Leader and former Barnett Government Treasurer Mike Nahan said "giant departments" would reduce efficiency, cost jobs and affect services.

"Mark McGowan was elected on a platform of creating 50,000 jobs," Dr Nahan said.

"So far all he has done is destroy jobs and undermine the confidence of the Western Australian economy."

Mixed reaction from union

CPSU branch secretary Toni Walkington says the public service has been subject to constant restructuring. ( ABC News: Andrew O'Connor )

Community and Public Sector Union branch secretary Toni Walkington said its members would have a mixed reaction.

"We have an acknowledgment that the Barnett government mismanaged the public sector and that reforms are well overdue," Ms Walkington said.

"It's good to see that the reforms are being done on a basis of policy considerations of departments and areas that work together."

Ms Walkington said she did not welcome the job cuts, but respected the Government's approach.

"There is some pain associated with it but it far more effective and far better than better than arbitrary cuts like efficiency dividends."

Departments amalgamated; new ones created

Departments set to be amalgamated include Agriculture with Regional Development, Attorney-General and Corrective Services, and Local Government with Culture and the Arts.

The Departments for Child Protection, Housing and Local Government and Communities and the Disability Services Commission will be housed under the new Department of Community Services.

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The Department of Aboriginal Affairs will be scrapped, with its functions to be taken over by Premier and Cabinet.

New departments to be created include Jobs, Tourism, Science and Innovation.

"I've had numerous complaints that people and communities struggle when they have issues to get a single agency to assist," Mr McGowan said.

"Making them deal with a plethora of government agencies rather than one agency is wrong. Clearly we need to bring those agencies together and create a one-stop shop."

Nahan claims cuts won't help budget

Mr McGowan would not put a dollar figure on the savings the cuts would generate.

"There will be savings over time, we haven't put a figure on it but there will be significant savings generated," he said.

"It will ensure we get better, more efficient service delivery. It will make sure our public sector works more effectively and collaboratively."

However, Dr Nahan said the department cuts would fail to deliver Labor's projected savings.

"The only way you can get that much reductions in numbers of public servants is to impact essential services, teachers, doctors, police, educational assistance, child care, disability services," he said.

"In order to get to the $750 million savings indicated, you won't achieve that through these amalgamations."

WA's social services body welcomes move

WA Council of Social Services CEO Louise Giolitto said the merger would allow government departments to operate more efficiently.

"We're really waiting on the details to learn how this, how the mechanisms, and this will actually operate within the state government. It opens up the opportunity for collaboration across government," she said.

Ms Giolitto said protecting vulnerable people during the transition period was paramount.

"The risk during the transition is that we are going to lose sight of those most vulnerable in our communities, that we are going to be caught up in this wave of amalgamating government departments where there will be impacts on front-line services," she said.

The changes will come into effect on July 1.