City of Ottawa officials were busy taking down illegal campaign signs over the weekend that attack the Progressive Conservative party and its leader Tim Hudak.

The signs — spotted in the ridings of Ottawa-Orléans, Ottawa-South and Ottawa West-Nepean ​— read, "The numbers just don't add up. We can't trust Hudak and Ontario PCs."

illegal signs Working Families Ontario PC Tim Hudak

Illegal signs popped up in at least three Ottawa ridings over the weekend. (CBC)

City of Ottawa bylaws state that only election signs from registered political parties and their candidates are allowed but the union-supported group behind the signs argued it has a right to voice its opinion, too.

Patrick Dillon, spokesperson for Working Families, said Sunday that no one from the City of Ottawa has contacted the group about the signs.

"We don't have any plans to take them down, and we will continue to put 'em up until we're convinced that what we're doing is improper," he said.

Ontario PCs 'targeted,' candidate says

Hudak made a campaign stop Monday morning in Ottawa-Orléans, one of the ridings where illegal signs have been spotted.

PC candidate for Ottawa-Orleans Andrew Lister said the Working Families signs are a clear violation.

"They knew what they were doing was against the law in Ontario and in Ottawa, and they did it anyway," Lister said.

He said the illegal signs were strategically positioned next to his campaign signs.

"The more we drove around the riding, the more we saw them everywhere. And they always put them right beside my signs. Sometimes they put them under my signs," he said. "They were clearly designed to be targeted against the PC Ontario party."

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