Ontario Premier Kathleen Wynne's approval rating has plunged to just 12 per cent, according to a poll released Friday by the Angus Reid Institute.

It's a drop of four percentage points for Wynne since the polling firm's previous survey of Ontario voters, conducted in December. It is also Wynne's lowest-ever approval rating in an Angus Reid survey since she became premier.

Asked "Do you approve or disapprove of the performance" of Wynne, 81 per cent of those polled said they disapprove, while seven per cent said they were not sure.

The result "continues a very long and steady decline in approval" for Wynne since the fall of 2014, said Shachi Kurl, the polling firm's executive director.

"We tend to see premiers offering up their resignations or quitting politics when their approval levels get to this point," said Kurl. "However, the difference would be that Wynne appears to continue to have the support, at least publicly, of her caucus."

Earlier this week, a prominent Liberal urged Wynne to consider resigning and allow a new leader to contest the election, to be held June 7, 2018. Wynne has repeatedly said she intends to stay on for the campaign.

'We tend to see premiers offering up their resignations or quitting politics when their approval levels get to this point,' says Shachi Kurl, executive director of the Angus Reid Institute. (Twitter.com)

The poll was commissioned and conducted by Angus Reid as part of its regular quarterly polling of premiers' approval ratings across Canada.

It was conducted from March 6 to 13 — after the March 2 release of Wynne's plan to cut the average hydro bill by a further 17 per cent this summer.

"It could be that Ontarians simply haven't had the chance to really absorb the news and form an opinion on [the hydro plan]," said Kurl. "It may simply be that they are tired of what they're seeing and hearing [from Wynne] and they're simply feeling quite cynical."

The poll suggests the hydro issue is at the heart of Wynne's struggles.

It found 82 per cent of those surveyed oppose the sale of shares in Hydro One to private investors, while 74 per cent described their electricity bills as "very unreasonable" or "fairly unreasonable."

Hydro bills a crucial factor

Kurl called hydro "a major preoccupation" for voters and an issue that the Liberals "can't get away from."

Forty-three per cent of those surveyed said their household hydro bills will be one of the most important factors in deciding who to vote for in the election.

"One school of thought suggests that if voters are motivated by their own household's electricity bills, they will respond positively if the Wynne government is successful in reducing those bills," said the Angus Reid Institute in a news release.

"Another school of thought, however, suggests that the Wynne Liberals are already too damaged by the issue to regain trust on it."

The premier responded to questions about the poll during a press conference Friday with Brad Duguid, Ontario's Minister of Economic Development and Growth. Wynne said she is focused on doing the job she was given by the people of Ontario.

"I'm really focused on working with my team to make sure that, for example, people can pay their electricity bills; for example, that we have a strong auto sector in Ontario in a time of uncertainty," Wynne said. "Those are the things that are preoccupying me because that's the job."

The online poll surveyed 804 Ontarians from a representative randomized sample of 5,404 Canadian adults who are members of the Angus Reid Forum. A probabilistic sample of that size would yield a margin of error of +/- 3.5%, 19 times out of 20.