A new light rail project for the City of Ottawa is already $100 million over budget, but that estimate is expected to climb even higher.

A source told CTV Ottawa on Wednesday that technical problems for a light rail line to the city's east end are pushing the project's budget about 25 per cent higher than originally expected. The city has also underestimated the costs of a maintenance yard and transit platforms.

Those rising costs are raising red flags at the Ontario legislature, where the province's municipal affairs minister says the province needs a firm price tag before moving forward with the project.

"Every time the price goes up, that affects tax dollars and we've been asking the city to nail down those prices and give us firm estimates and let us know what the final cost is going to be," said Jim Watson.

If the city wants the federal and provincial governments to become equal partners, Watson said the city needs to have a concrete price for the project.

An integral part of the city's transit plan includes constructing a downtown tunnel, as well as an east-west light rail line from Blair Road to Tunney's Pasture. The cost of phase one for the transit plan is now nearing $2 billion.