TORONTO -- Complaints about billing errors and poor customer service by Hydro One prompted Ontario Ombudsman Andre Marin to launch an investigation Tuesday into the government-owned electrical utility.

"This investigation is the result of years of behind-the-scenes efforts by my staff to resolve hundreds of complaints, one case at a time," said Marin. "We've worked with Hydro One to ensure they credit people who were over billed and don't cut off power to people in need, but the complaints have continued to increase."

Marin's staff got "the runaround" and experienced "stonewalling" from Hydro One, the huge power transmission agency that also serves as a local electricity distributor for more than 1.2 million customers in smaller and rural communities.

"Sometimes it's like wrestling with a slippery pig," said Marin. "That's why my heart goes out to those average citizens who try to take on the Goliath that is Hydro One."

Hydro One admitted it was not providing adequate customer service, which it contracted out to call centre operator Vertex, and said it would provide more training for the Vertex staff who answer the Hydro One phones.

"We know that the level of service we've been providing to customers is not acceptable," said Hydro One spokeswoman Tiziana Baccega Rosa. "It's not what they deserve, and it's not what we want to give them."

The Ministry of Energy also admitted Hydro One had problems with customer service, and promised full co-operation with the ombudsman's investigation.

"This level of service isn't acceptable and Hydro One has been working to address outstanding issues as quickly and efficiently as possible," said ministry spokeswoman Beckie Codd-Downey.

Marin took a shot at the Liberal government's time-of-use pricing for electricity when he complained about Hydro One's lousy customer relations and bad billing practices.

"We are hearing from the public that they are quite prepared to be socially re-engineered as electrical trained seals, doing the laundry at certain times to avoid excessive billing, but on the other hand they want to be able to understand their billing," he said. "They want accuracy in their billing."

The ombudsman detailed complaints from customers who said their "bills are wrong, excessive, duplicated, unreasonably delayed or estimated based on unclear criteria." Others were hit with huge catch-up bills that put them into overdraft after Hydro One took the money directly from their bank accounts.

"People wake up with $10,000 or $20,000 skimmed off their bank account by error, they didn't owe that money," said Marin.

The Progressive Conservatives and New Democrats both welcomed Marin's investigation, saying they've been bombarded with complaints from Hydro One customers who can't get anywhere when they try to deal with the utility.

"My attempts to have these problems rectified from within Hydro One have proven fruitless, as there is either an unwillingness or inability within Hydro One's bureaucracy to address the problems plaguing so many of my constituents," said PC critic Randy Hillier.

NDP Leader Andrea Horwath said complaints about Hydro One's billing practices have been building for years, especially when some customers go up to a year with no bills and then get hit with a huge invoice based on 'estimated' usage.

"This investigation will, I hope, get to the bottom of why these bills are so out of whack," she said. "There's something amiss at Hydro One."

Marin said he expected his investigation into Hydro One to take nine months.