Former WA treasurer Troy Buswell's chief of staff attempted to deliberately conceal crucial details about her boss's late night crash in a ministerial car, a report by the state's corruption watchdog has found.

Key points: Mr Buswell's chief of staff misled government about her boss's car crash

Mr Buswell's chief of staff misled government about her boss's car crash CCC report found she engaged in misconduct

CCC report found she engaged in misconduct Also recommended his electorate officer be investigated by DPC

Also recommended his electorate officer be investigated by DPC CCC 'formed no opinions' about Mr Buswell's conduct

Mr Buswell resigned as Treasurer in the wake of an incident in which he smashed into several parked cars while driving to his Subiaco home from a wedding in King's Park.

But while the commission formed no opinion about his conduct, it concluded his chief of staff Rachael Turnseck deliberately misled the Premier, an internal government inquiry, the Parliament and the commission itself.

Despite being aware of the incident on the day it occurred, neither Ms Turnseck nor Mr Buswell reported the full details until it became public through media reports on March 9, 2014.

Instead, the CCC said Ms Turnseck had emailed the Premier's Chief of Staff, Brian Pontifex advising "Troy is unwell so will not be at cabinet tomorrow or Parliament on tues (sic)."

In the days after the crash, she continued to withhold details, telling Premier Colin Barnett the treasurer had experienced some kind of mental breakdown.

"In the commission's opinion Ms Turnseck was unable to satisfactorily explain why she did not mention to the Premier the fact that Mr Buswell had crashed his ministerial car, had consumed alcohol prior to the accident and that his vehicle was badly damaged," the CCC report said.

When those details became public, the Department of Premier and Cabinet conducted an internal inquiry which found Ms Turnseck's decision not to report the accident immediately was "influenced by her focus on protecting Mr Buswell from self-harm".

The internal inquiry found that she should not be subject to disciplinary action.

CCC findings contradict government's internal review

In Parliament today, the Opposition targeted Premier Colin Barnett over the stark contrast between his department's findings, and opinion of the CCC that she had engaged in misconduct by giving false and misleading information.

Key moments in Buswell's career February 26, 2005: Elected to represent the seat of Vasse.

February 26, 2005: Elected to represent the seat of Vasse. January 17, 2008: Assumes leadership of the WA Liberal Party. Accused of snapping the bra strap of a female Labor staffer, and also admitted making a sexist remark to a fellow MP.

January 17, 2008: Assumes leadership of the WA Liberal Party. Accused of snapping the bra strap of a female Labor staffer, and also admitted making a sexist remark to a fellow MP. April 29, 2008: Tearfully acknowledges sniffing the chair of a female staffer in late 2005.

April 29, 2008: Tearfully acknowledges sniffing the chair of a female staffer in late 2005. August 4, 2008: Resigns as Opposition Leader in the "best interests of the party" one month before state election.

August 4, 2008: Resigns as Opposition Leader in the "best interests of the party" one month before state election. September 6, 2008: Liberals defeat incumbent Labor party at election.

September 6, 2008: Liberals defeat incumbent Labor party at election. September 23, 2008: Appointed to Cabinet as Treasurer, Minister for Commerce, Science and Innovation, Housing and Works.

September 23, 2008: Appointed to Cabinet as Treasurer, Minister for Commerce, Science and Innovation, Housing and Works. April 27, 2010: Steps down after allegations he used public funds to arrange meetings with lover and then Greens MP Adele Carles. However, both were later cleared.

April 27, 2010: Steps down after allegations he used public funds to arrange meetings with lover and then Greens MP Adele Carles. However, both were later cleared. December 14, 2010: Elevated back to Cabinet as Minister for Transport, Housing, and in July 2012 regains Treasury portfolio

December 14, 2010: Elevated back to Cabinet as Minister for Transport, Housing, and in July 2012 regains Treasury portfolio February 8, 2014: Settles defamation case against former partner Adele Carles.

February 8, 2014: Settles defamation case against former partner Adele Carles. March 10, 2014: Resigns from Cabinet after what Premier Colin Barnett describes as a "breakdown" amid reports he was involved in a car crash before taking personal leave.

Mr Barnett said Ms Turnseck had attempted to protect Mr Buswell's health in a very difficult situation.

"There is no doubt that Rachael Turnseck found herself in a situation where she was predominantly concerned about his health," Mr Barnett said.

"I can assure you he was in a very serious situation, extremely serious, ... that may well have clouded the judgement, particularly of Rachel Turnseck."

But the CCC questioned the accuracy of Ms Turnseck's claims.

In her initial evidence to the Commission, she had claimed she went to his house on the morning of the crash, to find him "very distressed and agitated" and that she was "very concerned for his welfare".

"These statements were misleading," the report said.

"Mr Buswell gave evidence that he left his home with Ms Turnseck, who drove him to her residence where she provided him with use of her vehicle," the report said.

"When recalled for further examination, Ms Turnseck changed her account."

The commission said she had provided misleading information on that issue to the department's internal inquiry.

"One substantial omission made by Ms Turnseck was in relation to her government vehicle loaned to Mr Buswell on the afternoon of 23 February," the report said.

"This was relevant to Ms Turnseck's opinion of Mr Buswell's mental impairment and formed the basis (and justification) for her subsequent actions," the report said.

In fact, Mr Buswell told the commission he had used Ms Turnseck's car to go to lunch with his children and then retrace his crash route through Subiaco.

The commission concluded lending Mr Buswell her car and letting him travel unaccompanied cast serious doubt on Ms Turnseck's claims her failure to immediately report the full details of the incident were the result of her concerns for Mr Buswell's mental health.

"Those actions are inconsistent with any concern that Mr Buswell was showing signs of potential self-harm," the report said.

Troy Buswell's damaged ministerial car was towed from his Subiaco home in March, more than a fortnight after the crashes. ( Supplied: Channel 7 )

"For Ms Turnseck to act in such a manner, rather than seek immediate medical care for Mr Buswell, is also at odds with the conclusions drawn by Mr [Tim] Marney [WA Mental Health Commissioner] who, relying on Ms Turnseck's description, concluded that Mr Buswell had suffered a major mental crisis.

"Any remaining doubt about Ms Turnseck's account in this regard is directly contracted by Mr Buswell's own evidence."

The CCC also recommended the conduct of Mr Buswell's electorate officer, Leo Gibbons, be investigated by the Department of Premier and Cabinet.

"Since the provision of the report to me, Mr Gibbons' employment within government has ceased," Mr Barnett said.

Mr Barnett said the commission formed no opinions about Mr Buswell's conduct, given he had accepted responsibility, left public office, and had a significant health condition.

He said he had accepted the commission's findings and "the lessons it highlights will be learned".