The price tag of the proposed LRT tunnel is a big issue on Ottawa's municipal campaign trail. If it happens, it could make history as the biggest project ever taken on by the city.

Some candidates are questioning the cost.

"Downtown tunnel and LRT will raise property taxes 16 per cent," says mayoral candidate Mike Maguire. "I think the downtown tunnel in terms of expenditure at this point is a terrible idea."

Maguire has launched a series of radio ads targeting property taxes and the proposed downtown tunnel. He says the $2.1B project, which covers the entire transit plan, will absorb infrastructure money for an entire generation.

Allan Hubley is vying for a seat on council, and shares his concern. "We support the vision of light rail but we want to see the tenders. We want to see what the final costs are going to be."

Hubley says, if elected, he would work on extending the transitway to Scotiabank Place in Ottawa's west end.

Meanwhile, Stephen Blais is running for councillor in the east end. He says the project should work on linking all ends of the city together.

"We've got the highest ridership of OC Transpo in this city and it's going to be 25 to 30 years before the residents of Orleans and Cumberland can benefit from a multi-billion dollar train plan."

Rival mayoral candidates Jim Watson and Larry O'Brien both support a light rail tunnel. Andrew Haydon wants one for buses.

With a report from CTV's Karen Soloman