The WA Government's hopes of reappointing state anti-corruption boss John McKechnie are hanging by a thread, with the Liberals and Nationals vowing to oppose "unprecedented legislation" to extend his term.

Key points: A parliamentary committee refused to ratify Mr McKechnie's reappointment

A parliamentary committee refused to ratify Mr McKechnie's reappointment It comes after the CCC exposed the misuse of electoral allowance funds

It comes after the CCC exposed the misuse of electoral allowance funds WA's Opposition says the change is not in line with anti-corruption practice

Mr McKechnie is almost certain to be without a job in a fortnight, with a political stalemate over his reappointment deepening after the decision by the Liberals and Nationals to oppose an overhaul of the way the Corruption and Crime Commissioner is appointed.

It means the only way Mr McKechnie can be reappointed is if Labor wins enough support from the Greens and key crossbenchers to get that legislation through, or a parliamentary committee overturns its objections to extending his tenure.

The Government needs five of the nine Greens or crossbench MPs to back the bill — one has already said he would oppose it while One Nation, which has two of those MPs, has also strongly criticised the plan.

Mr McKechnie's term as head of the Corruption and Crime Commission (CCC) expires on April 28, with hopes of his tenure being extended before then having significantly faded.

Under Mr McKechnie's time in the top job, the CCC has uncovered some of the biggest public sector corruption scandals, including within the Department of Communities and the North Metropolitan Health Service.

The CCC also last year released a report into the alleged misuse of electoral allowances in the WA Parliament — which detailed how former Liberal MP Phil Edman used taxpayer funds to pay for strippers and travel for sex.

The Government wants to reappoint Mr McKechnie but his contract renewal failed to receive majority and bi-partisan support from the Joint Standing Committee on the Corruption and Crime Commission.

The committee is made up of Labor MPs Margaret Quirk and Matthew Hughes, Liberal MP Jim Chown and Greens MP Alison Xamon.

It votes confidentially so it remains unclear who objected to Mr McKechnie's appointment.

Opposition Leader Liza Harvey said the Premier should work with the committee rather than changing the law. ( ABC News: Armin Azad )

Before the Liberal Party confirmed its position, leader Liza Harvey said the legislation would be a "nonsensical" approach.

Ms Harvey said she supported Mr McKechnie's reappointment, but changing the act was not the right way to keep him in the job.

"I don't know if the Premier [Mark McGowan] has gone back to that committee and said 'can you please explain to me why you haven't supported Mr McKechnie's appointment — what is the road block here'?" Ms Harvey said.

"He's just had a dummy spit because he didn't get his own way and now he's looking at changing the act."

Opposition harks back to dark 'WA Inc' days

In a statement, Ms Harvey said the new legislation would vest too much power in any future premier to appoint their own corruption watchdog.

"These proposed laws will give the Premier — any premier now or future, honest or corrupt — the ability to choose the top corruption fighter in WA. That is dangerous. It goes against all good anti-corruption practices," she said.

"The process currently enshrined by law was put in place by Labor in the shadow of its WA Inc days."

WA Inc was the subject of a royal commission in the early 1990s, and refers to a series of deals struck with big business figures like Alan Bond and Laurie Connell by the then-Labor government under Brian Burke.

The Government's proposed changes would see the commissioner's appointment require majority and bi-partisan support of the whole Parliament, and not just the committee.

Parliament was recalled on Wednesday from its five-week break to deal with urgent COVID-19 related legislation, and the Government hoped to deal with the CCC matter then too.

The Government now needs the support of five Upper House MPs.

Shooters, Fishers and Farmers Party MP Rick Mazza said he would opposed the bill, while One Nation leader Colin Tincknell tweeted the Government had "no right to change a system put in place by a Royal Commission to avoid another WA Inc".

The Greens position is not yet clear.