Victorian Premier Denis Napthine appears to be taking a tougher stance on maverick balance-of-power MP Geoff Shaw’s misuse of his parliamentary car, saying he will ensure Mr Shaw’s “wrongful behaviour” is dealt with urgently.

Dr Napthine’s comments come after Mr Shaw withdrew support for the Napthine government and as Labor continues to threaten to have Mr Shaw found in contempt of parliament over the parliamentary car issue.

The Victorian government is unlikely to be brought down by Mr Shaw’s sudden announcement on Tuesday that he would support any vote of no confidence against the government, with Labor shying away from such a motion.

Dr Napthine, who had relied on Mr Shaw’s support to hold power, on Wednesday strengthened his stance about Mr Shaw, who was found by a government-dominated parliamentary privileges committee to have misused his parliamentary CAR and fuel car to aid his private hardware business.

“Mr Shaw’s wrongful behaviour will be dealt with and will be dealt with appropriately, strongly and effectively,” he said.

Last week, the committee ordered Mr Shaw to repay more than $6000 but recommended no further action against him, incensing Labor.

A minority committee report from its Labor members recommended Mr Shaw be found in contempt of parliament.

Opposition Leader Daniel Andrews re-stated his aim to have Mr Shaw found in contempt and expelled when parliament resumes on Tuesday.

“I’m not prepared to have Geoff Shaw run our state,” Mr Andrews said on Wednesday.

“We can deal with him once and for all and we can end this circus.”

Mr Andrews says a by-election in Mr Shaw’s Frankston seat could occur as early as July 12 or 19.

He did not believe it a waste of money so close to the November 29 poll.

Mr Andrews has not ruled out moving a no-confidence motion in the government, at some point, but said he won’t be doing any deals with Mr Shaw.

Labor has the backing of Ken Smith, the former Liberal Speaker Mr Shaw helped oust, in its bid to have the Frankston MP held in contempt.