Former WA treasurer Troy Buswell has quit politics.
Mr Buswell handed his resignation to Speaker of the Legislative Assembly, Michael Sutherland, on Wednesday.
"I had a visit from Troy Buswell today at about 11.30 at Parliament House and he handed me his letter which was his resignation from Parliament," Mr Sutherland told the ABC.
"His resignation is effective immediately and things will have to be put in train to hold a by-election in Vasse."
The colourful Member for Vasse was forced to resign from Cabinet following a series of car crashes as he drove his ministerial vehicle home from a wedding in February.
In the wake of the incident Mr Buswell relinquished both his Treasury and Transport portfolios, and was fined $3,000 and suspended from driving for a year.
He suffered a breakdown and took some time off work before returning to Parliament in May.
Mr Buswell later revealed he was suffering from bipolar disorder and depression.
Mr Sutherland said Mr Buswell's letter did not give details of why he was resigning.
"I think it was a very pleasant letter thanking his colleagues and saying it was a great honour for him to have served the people of Western Australia," he said.
Mr Sutherland said Mr Buswell had been an outstanding minister but had gone through a difficult time.
"I think it's like a Greek tragedy because we all know that he was a very talented person, he is a very talented person, and it's a pity that he's been lost to public life," he said.
"Considering the circumstances, I think that we can understand why he's resigned. But I think if the circumstances had been different he would have a really big part to play in the politics of the future."Resignation triggers by-election
His resignation will prompt a by-election in the safe Liberal seat in WA's south-west.
Mr Buswell has held the seat of Vasse since 2005 and became the deputy leader of the Liberal Party in the same year.
He was opposition leader from January to September 2008, and has been twice been treasurer.
However, his career in politics has been marred by indiscretions.
He was forced to resign as the leader of the WA Liberal Party in 2008 after admitting he sniffed the chair of a female staff member and snapped a Labor staffer's bra.
Mr Buswell was appointed to the frontbench under Mr Barnett.
He stepped down as treasurer in 2010 after allegations surfaced that he used public funds to arrange meetings with lover and then Greens MP Adele Carles.
Mr Buswell and Ms Carles were both cleared of misusing ministerial entitlements in June 2010 and Mr Buswell returned to the frontbench in December.
He was advised by Premier Colin Barnett when appointed treasurer that he was on his final warning.
Last year, Mr Buswell denied trying to hide a controversial budget decision involving the WA Insurance Commission, which allowed the Government to take up to 65 per cent of the commission's profits.By-election could be opening for Birney: analyst
Ian Cook, a senior politics lecturer at Murdoch University, said Mr Buswell was ambitious and many people thought he would stay in politics until he became premier.
"Despite the fact he's attracted controversy and hasn't always acted as well as we might have hoped in the position, he was still a strong performer within the Liberal Party and the Liberal Party has lost someone who can pull them forward and bring them together," Dr Cook said.
"It's bad for the party and for WA politics generally."
He said the Vasse by-election would be closely watched and could be an opening for former Liberal leader Matt Birney, who last week announced his intention to return to politics.
"Colin Barnett is struggling to some extent," he said.
"This is going to be a really important test for his government and we're all going to look for it closely and if the messages are negative the Liberal Party will really have to start thinking about what its future is and who its future leader is.
"The pressure is now absolutely extreme on the party, they've got to come up with the next person and start grooming that person.
"I think it is potentially an opening for Matt Birney, whilst we've struggled to come up with people who could fit the bill in some ways he's positioned.
"He's not old school, he doesn't carry too much baggage."