Ontario's Ombudsman has announced plans to conduct a "systemic investigation" of complaints about billing practices and customer service at Hydro One.

"In the past few years, we have seen more and more complaints from Hydro One users about bills that seem to have no bearing in reality -- and about the lack of answers they get when they ask why," Ombudsman Andre Marin said in a statement Tuesday.

The number of complaints have doubled since 2011-2012, when Marin's office fielded 232 customer concerns about the government-owned electricity transmission company.

Between April 1, 2013 and today, Marin's office reports fielding more than 600 complaints, most of which focus on billing issues.

Besides "wrong, excessive, duplicated, (and) unreasonably delayed" bills, Marin highlights frequent complaints about costly "catch-up" bills issued to customers who have not been billed in a long time.

“People wake up with ten, twenty thousand dollars skimmed off their bank account by error - they didn’t owe that money,” Marin said at a press conference Tuesday morning.

“So it’s leaving a bad taste in the mouths of citizens of Ontario.”

In a statement released Tuesday, New Democrat Leader Andrea Horwath said Hydro One errors are “just another example of a hydro system that isn’t working” for families and businesses struggling to pay the bills.

“Instead of taking action to solve the issue, the government denies there’s a problem while more and more families get stuck with massive bills,” she said.

Horwath said former Liberal Energy Minister Brad Duguid had insisted that Hydro One billing errors would be resolved after the NDP leader called on the Ombudsman to investigate the issue in 2010.

But the problems have only gotten worse, Horwath said.

“This issue is not only affecting family homes -- small businesses across the province are being overbilled for power they aren’t using, and are at risk of shutting down their doors. Ontarians deserve better,” Horwath said.

A Hydro One spokesperson tells CTV Toronto the company acknowledges that their level of service is unacceptable and is working to fix the issue as quickly as possible.

After consulting with the public, Marin expects to produce a report and recommendations within nine months.

As Ontario's largest electricity company, Hydro One has approximately 1.4 million customers across the province.

Anyone with concerns about Hydro One service is asked to call the Ombudsman's office at 1-800-263-1830, email info@ombudsman.on.ca, or visit the watchdog's website.