West Australian taxpayers have forked out more than $5 million in payouts to senior bureaucrats amid a major overhaul of the public sector, with the figure set to rise substantially in the coming months.

Eighteen senior executives, who either have left the public service or will do within the next month, have split $5.1 million in payouts from the WA Government since May.

The biggest of those are $424,591 to Ruth Shean, the ex-director general of the Department of Training and Workforce Development, and $419,191 to outgoing Disability Services Commission boss Ron Chalmers.

Richard May (Premier and Cabinet, $376,046), Jim Sharp (Parks and Wildlife, $372,423), Jo Harrison Ward (Public Sector Commission, $371,400) and Emma White (Child Protection, $355,695) also received hefty payouts, while five others received more than $200,000.

It is understood those amounts only represent compensation payments and do not include leave or other entitlements the departing executives have been paid.

Another 21 executives, whose positions were abolished due to the public sector changes, remain in limbo but are still employed by the Government.

That includes the likes of Ron Alexander, Gail McGowan and Duncan Ord, who had all previously been serving as departmental heads.

The payouts come amid an exodus of senior public servants since the McGowan Government announced its public sector overhaul, which came into force on July 1.

Those changes have reduced the number of government departments from 41 to 25, which Premier Mark McGowan promised would produce a cheaper and more efficient public service.

Payout figure set to rise

The Government promised 20 per cent of the then 521-member senior executive service would go, meaning the payouts revealed so far would represent just a fraction of the eventual cost.

The figure also does not include executives who have been redeployed to the Public Sector Commission, following the abolition of their own roles.

Despite the payout cost, Acting Premier Roger Cook said taxpayers would still benefit from the public sector reforms in the long term.

"There is a certain amount of expense that goes with reducing the number of senior executive service public servants, these are highly paid public servants," Mr Cook said.

"But that doesn't mean you don't take action ... we have to act on these things because we have to make sure our public sector works better for Western Australia."

Mike Nahan says the reform process has been chaotic. ( ABC News: Jacob Kagi )

More than two months after announcing the reforms, the McGowan Government has still not revealed the total number of expected job losses or the forecast long-term saving.

Opposition Leader Mike Nahan said the public sector needed reform but described the current process as "chaos".

"It needs to go through that in a systematic manner to ensure you have the best people and the best structures," Dr Nahan said.

"We need the best and I am afraid some of the best are going here."