A group called Toronto Street Advertising Takeover (TOSAT) exchanged ads for arts on 41 billboards this Sunday. (Susan Noakes/CBC)Members of a group of activists calling themselves Toronto Street Advertising Takeover papered over advertising with art throughout the city this weekend.

The group (TOSAT), which invited some media outlets to witness their activities, said they were taking back public space from illegal ads.

Members of the guerrilla group took covers off standing billboards and papered ads over with graphic art, paintings and anti free-market sketches.

The art attack affected 41 advertising pillars, and 20 to 25 larger billboards, many of them owned by Pattison Outdoor Advertising.

TOSAT organizers claimed they specifically targeted ads that were illegal.

On Monday, Jonathan Goldsbie, a member of the Toronto Public Space Committee, defended their actions.

Goldsbie's non-profit group is unrelated to the art activists, but also has an interest in protecting the city's shared common spaces and has been involved in Toronto's efforts to change ad bylaws.

He told CBC News he believes many of the signs papered over with art may well have been illegal.

"Pattison and other companies have spent decades putting items in the public space, and doing so very frequently illegally. These are companies that have planted the items often without permission, often with deliberate disregard to the law, with contempt for council, with contempt for the citizens of the city," he said in an interview Monday.

Activist group TOSAT claimed members papered over ads that were illegal. (Susan Noakes/CBC)"So actions like this one are partially an act of reclamation. It's a matter of saying for whatever reason, the city has been thus far ineffective in enforcing its own bylaws, therefore we're going to go out and be the change we want to see."

Last December, the city created new ad policy and laws that provide for more effective enforcement. The bylaw includes a billboard tax.

Ad companies suing city

Goldsbie said he is concerned that the city, while it has improved enforcement since April when the bylaw came into effect, has yet to have an impact on illegal ads.

"In the meantime, advertisers continue to make millions of dollars with ads that they put up with knowing disregard for the law," he said.

A group of ad companies is suing the city over the new bylaw, Goldsbie said, adding that ad companies probably hope they can force concessions from the city.

The TOSAT campaign was similar to an ad attack mounted in New York last year and involved art donated from Spain, Berlin, California and throughout Canada.

There were arrests in the New York campaign, but the Toronto activists appeared to have worked without police interference.