TORONTO -- Ontario's opposition parties said Wednesday they are being flooded with complaints about "outrageous" over-billing and poor customer service at government-owned Hydro One, and demanded the utility's CEO be fired.

A family-run grain elevator in the London area that usually pays at most $4,500 a month for electricity got a three-month "estimated" bill from Hydro One for $233,693.70, said Progressive Conservative Jeff Yurek.

It's the worst example so far of seemingly unexplainable Hydro One bills that constituents call in every day to complain about, and shows CEO Carmine Marcello cannot get a handle on the billing and customer relations problems, said Yurek.

"Previous to this they had a $7,000 credit because of over-billing from Hydro One, and then they get nailed for $233,000," he said. "It's obvious that the culture of Hydro One isn't one of customer service or of care, and I can't see that changing with the CEO who created the culture staying in place."

The family who got the huge bill doesn't want to go public, but reporters were given copies of their Hydro One statement, which showed an estimated usage of 22,442 kilowatt hours of electricity for 86 days, compared with their normal 400-to-500 kWh "actual" monthly usage on previous bills.

"I don't know about you, but if I'd opened up a bill for $233,000 from Hydro One you'd be picking me up off the floor," said Yurek.

The New Democrats also reported their constituency offices are getting calls from customers concerned about their Hydro One bills and said they supported the call for Marcello's resignation.

Hydro One admitted it "had caused a number of our customers some angst" as it implements a new billing system, but said it had dealt with the original complaint raised by Yurek's constituent within 10 days last fall and straightened out the billing situation for the grain elevator.

"The initial bill was sent in error, but the correct bill was immediately sent to the customer and since then the customer has received the correct bills," said Hydro One vice-president Laura Cooke.

The Liberals said Yurek was "more interested in playing political games than resolving a legitimate customer concern" because he didn't raise the huge bill with Hydro One officials when they were in contact with him on Tuesday.

"The CEO (of Hydro One) has publicly apologized and is taking strong action to address these customer concerns," said Beckie Codd-Downey, press secretary to Energy Minister Bob Chiarelli. "We are confident in the CEO at Hydro One that he will resolve these issues."

The Opposition does not share the government's confidence in Marcello.

"If this were the private sector he'd be thrown out," said Yurek. "You can't change the culture of Hydro One keeping the man that created the culture and let it grow and fester, you can't keep him in place and expect a change."

Ontario ombudsman Andre Marin launched a formal investigation into Hydro One's billing practices after getting hundreds of complaints, and said his investigators "got the runaround" and experienced "stonewalling" from the utility.

Marin's office said Wednesday it has since logged 6,161 complaints about Hydro One, the highest number ever received about a single government organization.

Yurek also said appointing former Liberal cabinet minister Sandra Pupatello to chair the Hydro One board won't change anything because she was part of the government that approved the new billing system, smart meters and the green energy act.

Hydro One is the province's electricity transmission utility, responsible for the wires that make up the power grid, but it also serves as the local power distributor for 1.2 million customers, mainly in remote and rural areas of Ontario.