The State Opposition is continuing its calls for Troy Buswell to resign from Parliament, saying the former treasurer could be charged with a drink-driving offence without an alcohol reading if he admitted to police that he had been drinking.
Mr Buswell, who was disqualified from driving for a year and fined $3100 on Tuesday after pleading guilty to 11 traffic offences, has not been interviewed by police.
Shadow attorney-general John Quigley said Mr Buswell was entitled to his right to silence as a citizen but as a lawmaker should be held to a higher standard.
He said there was capacity in the relevant legislation to charge someone with driving under the influence if they had not had a breath test.
He said a police prosecutor had contacted him and referred him to a part of the Road Traffic Act that said "it is possible, albeit increasingly rare in practice, to secure a conviction without any blood alcohol measurement".
"There is a strong prima facie case of driving under the influence of alcohol to the extent that he was incapable of proper control of the vehicle," Mr Quigley said.
"The questions are, prior to driving that vehicle and being involved in five collisions, when were you consuming alcohol last, over what period of time and how much did you consume?
"If he (Mr Buswell) wants to put his individual rights above his public duty, then he shouldn't occupy public office."
After the revelations of Mr Buswell's accidents on February 23, Police Commissioner Karl O'Callaghan said it would be hard to prove a drink-driving charge without a breath test.
Premier Colin Barnett maintained nothing was stopping Mr Buswell from staying on as an MP, saying he had not been charged with drink-driving and it would be inappropriate for him to interfere in the justice process.
"I don't excuse what happened and I'm not pleased about it but Troy did the right thing - he stood down from the very senior position," Mr Barnett said.