The Ontario Liberals have filed a complaint with Elections Ontario alleging possible "voter suppression" after letters were sent from Tory campaigns in two ridings — one in London, the other in Ottawa — containing mistaken information about where to vote in Thursday's election.

The Progressive Conservatives were forced to apologize Tuesday after they party said a campaign worker sent letters to homes in London North Centre that invited residents to vote on Thursday — in the wrong location.

The letters "may have caused some confusion for residents of 64 households in the riding," PC candidate Nancy Branscombe said in a statement. In an interview with CBC News, she called the incident a mix-up by volunteers on her campaign who mistakenly stuffed letters for friends and supporters into the wrong envelopes.

"I want to apologize for any convenience. We are contacting these household to clarify."

But later Tuesday, the party was forced to apologize again, when a Liberal supporter in the riding of Ottawa West–Nepean received a separate but similarly misleading letter.

The Liberals circulated a copy of one of the London letters sent to Mariam Hamou, a Liberal Party member in the area.

"I wanted to remind our friends and neighbours that this Thursday June 12th is Election Day," says the letter, which appears to be signed by Tim Gatten, a constituency assistant to the riding's Conservative federal MP.

"This election my wife and I are planning on voting together ensuring our voice will be heard.... Our plan is to drive together to the Ridgeview Community Church at 1470 Glenora Dr for the opening of the polls at 9 a.m.," it continues, with the church name, address and voting date in bold.

"Maybe we will bump into each other at Ridgeview Community Church!"

The Ottawa letter, a copy of which was also given to reporters by the Liberals, is from a constituent named Saxon Harding. It reads: "I will be voting on my way home from work, but well before the polls close at 9 p.m. I plan to just walk over to St. Paul High School.... I hope that you have a wonderful summer, and maybe we will bump into each other at St. Pauls."

The Liberals said the recipient's actual polling place is steps from her house, not at the St. Paul school.

CBC News contacted a woman named Saxon Harding who lives in the riding. She said, "Well, I let the party send that out," and then would not answer further questions.

The PCs later acknowledged in a terse news release that the second letter was also from their campaign.

"Today, we were made aware that letters to voters in the campaign may have caused some confusion for a small number of residents in the riding of Ottawa West Nepean," read the email from the Ontario PC Party. "We apologize for any inconvenience and have contacted these households to clarify."

PC Leader Tim Hudak was asked about the controversy on Wednesday morning in Mississauga and said the letters were the result of a "clerical error."

"Honest mistakes were made," he said. "Sometimes you don't have the right polling information and our candidates have apologized for that clerical error."

Hudak said the envelopes containing the letters stated they were "authorized by the PC party."

In a second complaint to Elections Ontario after the emergence of the Ottawa letter, the Liberals also suggest the Ottawa and London letters were sent from the same location.

"It appears from Canada Post's stamp that both the London North Centre letters and the Ottawa West-Nepean letter were routed through the same Toronto Canada Post centre," a letter from the party's lawyers says.

"The eerie coincidence of the text, the mailing from Toronto, and all of them having the wrong poll designated, they are eerie coincidences," said Bob Chiarelli, the Liberal candidate in Ottawa West-Nepean. "The voters deserve to know if this strategy is condoned by Tim Hudak's campaign."

PC spokesman Will Stewart told CBC News the party sends out "hundreds of thousands" of the so-called FRAN letters (friends, relatives and neighbours) every election.

Similar to Guelph robocalls, Liberals say

In their first letter to Elections Ontario, the Liberals note the recipient's correct polling place is at an elementary school about four kilometres in the opposite direction from the church location stated in the letter.

"There is the very real risk that, if Ms. Hamou were to leave her home to vote just prior to the close of the polls on the 12th, she would miss her opportunity to vote by virtue of the fact that she was directed to the wrong polling location," reads the complaint letter, written by lawyers for the party.

Mariam Hamou says she got this letter in the mail without a return address. The letter writer doesn't directly tell her where to vote, but mentions a wrong location nearly four kilometres away and the possibility of bumping into Hamou there.

"The above tactics are eerily similar to the Guelph robocall issue, currently at trial," the complaint says.

In the 2011 federal election, automated calls on voting day directed voters to the wrong polling station in the Ontario riding of Guelph. Michael Sona, a Conservative campaign worker, was later charged and his trial wrapped up last week. The judge has reserved his ruling.

The incumbent Liberal candidate for London North Centre, Deb Matthews, denounced the letters on Tuesday, saying "the notion that you misdirect voters to take away their right to vote is completely outrageous."

"It is completely unacceptable. It is immoral it is unethical and it is illegal," she said.

The Liberals say the letter from Branscombe's campaign echoes the wording of a letter sent out by Tory candidate Bart Maves during a byelection in Niagara Falls in February. That letter told some voters, "Our plan is to drive together to the Orchard Park School (7555 Montrose) for the opening of the polls at 9 a.m."

Orchard Park School is actually at 3691 Dorchester Road, or 5.8 kilometres to the northeast. The Maves campaign explained to a local Niagara radio station at the time that an "administrative error" caused the mistaken letters to be sent out.

Both the Niagara and London letters end with "I hope that you have a wonderful long weekend." The Niagara byelection preceded a long weekend; this week's general election does not.

Elections Ontario stays mum

The Liberals' complaint to Elections Ontario questions whether two similarly worded letters could be mere mistakes. "We... are most concerned that this constitutes a deliberate attempt at voter suppression," the party says.

Elections Ontario would not confirm whether it has received a complaint or whether it is investigating.

Spokesman Peter Berry said that in general, when the agency gets a complaint, "it is reviewed by Elections Ontario and may be investigated. If the chief electoral officer believes there may have been an apparent contravention of the law, he is required to refer the matter to the Ministry of the Attorney General," who can forward it to police for further investigation and prosecution.

PC candidate Branscombe is seeking to unseat three-term Liberal incumbent Matthews in London North Centre. Matthews defeated Branscombe in the 2011 election with 44 per cent of the vote to Branscombe's 29 per cent.

In Ottawa West–Nepean, the Tories' Randall Denley is taking another run at Liberal Bob Chiarelli. Chiarelli defeated Denley by just over 1,000 votes in 2011.

It is an offence under Ontario's Election Act if someone "prevents another person from voting or impedes or otherwise interferes with the person’s exercise of the vote." The maximum penalty, if the offence was committed knowingly, is two years in jail and a $25,000 fine.