Google says it can't guarantee that it won't end up publishing campaign ads during the upcoming federal election, despite its announcement that it's banning political and issues ads during the election because of changes to Canada's laws.

Colin McKay, head of public policy and government relations for Google Canada, said the company is taking steps to prevent political ads from running during the election and is changing its ad policy. He said Google's ad systems are complicated and there isn't enough time before the pre-writ period starts to build the ad registry now required by federal law.

McKay said he has to be pragmatic, however.

"There's always a possibility that something might slip through," McKay told reporters.

If an advertiser evades Google's campaign ad ban and manages to publish a political ad, Google will work with the Commissioner of Canada Elections office "so they can take enforcement action," he said.

Keeping an eye out for rogue ads

If an advertiser keeps publishing ads on the site, it could be barred from running Google ads entirely, he said.

"We take the ad down and if we see repetitive behaviour that violates our policies, we then block the advertiser from accessing our systems and placing those ads."

Google will be using both machines and teams of staff to detect political ads.

"We will be applying that ads policy ... by both doing automatic filtering as well as human reviewing and taking them down as quickly as we see them," McKay said.

The biggest challenge will be identifying 'issues ads' — advertising that isn't connected to a particular party but advocates particular policies during the campaign period. Such ads also have to be reported through ad registries under Canada's new campaign advertising law.

McKay and Jason Kee, Google Canada's public policy and government relations counsel, were on Parliament Hill Thursday to face questions from Parliament's access to information, privacy and ethics committee about why Google has chosen to not accept political ads during the election, instead of setting up a registry of online advertising provided for in the new elections law.

MPs grilled McKay and Kee over the company's decision, suggesting at one point that Canada just isn't important enough for Google to take the steps called for in the elections law.

McKay and Kee countered that Google is passing up the revenue that would come from political advertising while donating money in Canada to improve news literacy.

A recent investigation by CBC News revealed that Google isn't the only company that won't be running political ads during the election and the pre-writ period which begins June 30. Only three of the 20 most popular online sites in Canada are planning to accept political or issue ads and set up ad registries: Facebook, Instagram and CBC.ca.

As of May 1, Twitter and Yahoo were still trying to decide whether they would accept Canadian election ads.

Elizabeth Thompson can be reached at elizabeth.thompson@cbc.ca

CBC Politics' new weekly Canada Votes newsletter

Get analysis from our Parliamentary bureau as we count down to the federal election. Delivered to your inbox every Sunday evening – then daily during the campaign. Sign up here