Western Australia's Attorney-General has launched an extraordinary legal action against the president and clerk of the Legislative Council in what he says is a bid to protect the state's corruption watchdog's investigation into a number of former MPs.

Key points: The CCC have demanded Parliament hand over emails, documents and data

The CCC have demanded Parliament hand over emails, documents and data They relate to an investigation into former politicians' travel allowances

They relate to an investigation into former politicians' travel allowances The Upper House has refused over concerns about parliamentary privilege

The WA Corruption and Crime Commission (CCC) has repeatedly clashed with the Upper House over its right to access emails and documents belonging to three former Liberal MPs as part of an investigation into electoral and other allowances.

The fight centres on whether the documents are subject to parliamentary privilege.

Two weeks ago the CCC issued "notices to produce" to Upper House clerk Nigel Pratt, ordering him to hand over emails, data and documents relating to travel allowances paid to the three former MPs.

But the Upper House passed a motion on Wednesday ordering Mr Pratt not to follow that directive.

Attorney-General John Quigley on Friday said he had issued a writ in the Supreme Court challenging that resolution.

"What's extraordinary in this … is that a committee of the legislative council is frustrating a very serious CCC inquiry into politicians," the Attorney-General said.

"This resolution was passed despite a previous report by the [committee] referring to an opinion from eminent QC Chris Zelestis advising that the Legislative Council did not have the power to order non-MLCs not to produce documents."

WA's Upper House is refusing to hand over former MPs' emails to the state's corruption watchdog. ( ABC News: Jonathan Beal )

The increasingly bitter stoush began in April when the CCC demanded the Department of Premier and Cabinet (DPC) hand over emails and documents relating to its investigation.

The CCC also seized a laptop and hard drive in a raid on the home of former Liberal MP Phil Edman.

The watchdog's demands became public last month, when the powerful Privileges and Procedures Committee released a damning report on the actions of senior bureaucrats in the Premier's department in relation to the CCC's demands.

The report said the committee had devised a method of dealing with how the CCC could access the documents without breaching parliamentary privilege, but then DPC staff stepped in.

It said the Premier's department chief, Darren Foster, and his staff applied their own sorting process and sent only certain documents to the CCC.

In another extraordinary development last month, Corruption and Crime Commissioner John McKechnie threatened to resign, and was summonsed to appear before the privileges committee.

'Big step' for AG to take

Mr Quigley said the issue would now play out "dramatically" on the floor of the Supreme Court.

"I can't think of another case where an Attorney-General has sued the president of the Legislative Council, and the clerk of the Legislative Council," he said.

"That is to me a big step to take.

"It was a step I've taken only after close consultation with the solicitor general of Western Australia, who is an independent office holder, and with the state solicitor, and of course with the Premier.

"You can't get more dramatic than that."

Mr Quigley denied lodging legal action naming his fellow Labor Party colleague and president of the Legislative Council Kate Doust would create friction in the party.

"Yesterday I discussed the Solicitor General's advice with the Premier, and the Premier said 'do your duty, Attorney-General'," Mr Quigley said.

"'Do your duty as you see it.'

"There is no rift in the Labor Party, this is the Attorney-General versus the Legislative Council over a dispute the council has with the CCC for whom I have ministerial responsibility."

Mr Quigley said he was left with "no alternative" as the state's law officer but to seek guidance from the Supreme Court.

"If the Legislative Council's resolution banning the clerk from cooperating with the CCC is valid, this may mean a chamber of Parliament can order anybody to not comply with investigations into corrupt politicians," Mr Quigley said.

"It would mean that a political party could use a majority in a chamber of Parliament to protect a corrupt colleague from investigation by the CCC."

Political commentator Peter Kennedy said the action was "unprecedented".

"This is an extraordinary standoff between the Legislative Council and the CCC," he said.

"It's a classic case of the separation of powers.

"Each organisation guards its powers very jealously and the Supreme Court could well come up with a precedent, so it's effectively democracy at work."