Under the changes, the jail term for leaving children unattended in vehicles rises from three months to six months and fines will increase from $2214 to $3690.

The tougher penalties were introduced by the previous Liberal government but were never proclaimed.

Premier Daniel Andrews said his government had moved to ensure the laws were in force by the end of January.

So far this year, there have been 23 cases of children being left in cars, including on days when the temperatures have exceeded 30C, Ambulance Victoria says.

Mr Andrews said many Victorians were failing to heed the warning, and paramedics attended to about 1200 children left in cars in 2013/14.

"It is completely unacceptable to leave kids in cars," he told reporters.

"The heat inside the vehicle can be double the temperature outside the vehicle in just a matter of minutes.

"This can cost a life."

Shadow attorney-general John Pesutto called on the premier to arrange an urgent meeting with the governor to have the new provisions proclaimed in coming days.

Statistics released by Ambulance Victoria last September showed paramedics attended 20 reports of children locked in cars in Bendigo in th 12 months up to August 31, 2014.

This included six reports in Bendigo and three each in Kangaroo Flat and California Gully.

- with AAP