The reduction in premiums was one of the NDP's budget demands and the party says they will not support the minority Liberals' budget unless the motion is passed.
"Ontarians' auto insurance premiums are the highest in Canada and they need to come down," NDP leader Andrea Horwath said.
"New Democrats have been very clear that we want to see a 15 per cent reduction."
The motion, calling for the province's insurance regulator to gradually cut the premiums, was presented Wednesday.
Premier Kathleen Wynne said she would support the motion.
"Because the underlying principle is we need lower rates for drivers in Ontario and that's what we're working on," Wynne said.
Although Wynne said the Liberal government would support the measures, such motions are non-binding.
Progressive Conservative insurance critic Jeff Yurek said his party will vote against it.
"We can't just support a motion that doesn't have a plan behind it, this is just bumper sticker politics," Yurek said.