John McKechnie's term as head of the Corruption and Crime Commission is due to expire on April 28.

The government wants Mr McKechnie to serve another term, but Liberal members of a parliamentary joint standing committee have declined to endorse his reappointment.

A leaked exchange of letters between Premier Mark McGowan and Opposition Leader Liza Harvey earlier this month revealed Ms Harvey had rebuffed the premier after he requested that she ensure the nomination had bipartisan support.

The government will this week introduce legislation to parliament which, if passed, will ensure Mr McKechnie is reappointed for a further five years.

"Mr McKechnie has the support of the state government, and is widely accepted by the public and the legal profession as the best choice to continue to lead the CCC ... he must be allowed to continue his important work," Mr McGowan said on Tuesday.

The stand-off comes as the CCC continues to investigate the misuse of electoral allowances by MPs.

A CCC report last year revealed former Liberal MP Phil Edman used his electorate allowance on acting as a "sugar daddy" to women he met online, visiting strip clubs and paying speeding fines.

It also included references to dinners held at taxpayers' expense by upper house Liberal MPs, who referred to themselves as the "Black Hand Gang", and a seized laptop containing damaging material.

"It's got everything, all the emails between all of us, Black Hand Gang dinners, it's got the video, there's enough stuff on that f***ing computer to bury f***ing a lot of people," Mr Edman was quoted as telling a former MP in the report.

Attorney general John Quigley said if MPs continued to veto Mr McKechnie's reappointment, it would be open to the public to infer they were doing so to "stymie his investigation of their expenses".

"This perception would bring state parliament into disrepute and cannot be allowed to stand," he said.

Australian Associated Press