Former WA treasurer Troy Buswell has revealed he suffers from bipolar disorder and apologised for his recent behaviour, in his first public comments about a series of car crashes that led to his resignation from Cabinet.

Speaking outside State Parliament today, he said he was "embarrassed" and "mortified" after crashing his ministerial vehicle into parked cars while returning home to Subiaco from a wedding in Kings Park in the early hours of February 23.

Last week, Mr Buswell was fined more than $3,000 and banned from driving for 12 months after pleading guilty to 11 traffic charges.

"I accept responsibility for my actions. I pleaded guilty and I paid the fine and I have no more comment to make in relation to events surrounding those matters," he said.

"I am embarrassed, in fact mortified that that happened and I have apologised and will continue to apologise to those people upon whom that impacted."

He said he was subsequently diagnosed with bipolar disorder and depression and would be receiving treatment for both.

Troy Buswell speaks publicly for the first time since the car crashes that led to his Cabinet resignation. ( ABC News: Andrew O'Connor )

Mr Buswell refused to answer questions about his drinking on the night of the incident or why he had not participated in police interviews, saying he had employed a lawyer who had done so on his behalf.

He said medical advice was that it was in his best interests to return to work but he did not respond directly when asked if he would serve out the full term in Parliament as Member for Vasse.

"What I can guarantee is that my focus is on getting better and my focus is on continuing to provide the very best level of service I can to my constituencies," Mr Buswell said.

Buswell's apology not accepted by everyone

WA's Opposition Leader Mark McGowan said Mr Buswell should have answered questions about whether he was drinking the night he crashed into a series of cars in Subiaco.

"I don't think Mr Buswell's explanation was good enough, he did not answer the questions," Mr McGowan said.

"The central question is how much did he drink before he drove home that evening and caused all of that damage and risked people's lives?"

Later in Parliament, Premier Colin Barnett said he had not asked Mr Buswell if he was drinking on the night of the crashes because it was not his job to investigate the incident.

Disgruntled Liberal backbencher Rob Johnson has labelled Mr Buswell's behaviour behind the wheel a "disgrace" and called on him to resign.

He said he was appalled and disgusted when several MPs applauded Mr Buswell during a party room meeting this morning.

Mr Johnson said Mr Buswell offered no explanation for the incident, telling the party room exactly what he had told the media minutes before.

Mr Johnson added the former treasurer was well-received by the majority of his colleagues.

"I say shame on some of them, they actually applauded him and I find that absolutely appalling that they would applaud somebody who committed those offences that could have killed somebody or put someone in hospital with critical injuries," he said.

"I have been inundated by people in my electorate who expect more from their MPs, and they are very, very dissatisfied with the way Troy Buswell has behaved."

Mr Barnett had urged Mr Buswell to provide some explanation to his parliamentary colleagues, and to front the media when he returned.

"I think he does have a responsibility to provide some account of what happened," he said.

Mr Buswell had previously not spoken publicly about the crashes, however he did release a statement following his guilty pleas.

"I offer no excuses for my actions, apologise to those upon whom I have impacted and accept fully the consequences," the statement said.

There have also been questions raised about the cost of Mr Buswell's trip to Europe last year to study light rail, during which he and his then chief-of-staff spent $14,000 while in France.