A crucial vote on the future of Ottawa's $6-billion light rail transit plan has passed, with city council approving the design of the plan and voting to move forward with an environmental assessment.

"I go into this vote light-hearted. I go into this vote with a sense of joy because we are doing the right long-term, we are making the right long-term decision for the City of Ottawa and this will expose us to many opportunities," Mayor Larry O'Brien told council.

"They will thank us in 2060, 2070 for the wisdom of this council, approving the functional design today, which will lead to a project in the next term."

Council voted 19-4 to approve the functional design of the plan and move forward with an environmental assessment of the project.

The first phase of the project is estimated to cost $2.1 billion, a price tag that has jumped from a previous estimate of $1.8-billion.

The phase includes building a downtown tunnel, and laying light rail tracks from Blair Road to Tunney's Pasture.

The newest mayoral candidate criticized the light rail plan when he announced his intentions to run for mayor on Tuesday.

Jim Watson told CTV Ottawa he's uncomfortable with the cost of the project. He said the vision for transit should be planned around the budget, "not the other way around."

At Queen's Park, Premier Dalton McGuinty weighed in on the issue, saying it's up to the people of Ottawa to decide what kind of transit plan they want.

"We've committed to a plan in principal, but in terms of the specific details, where the specific routes are going to run, that's not something that we've agreed upon in any kind of form," said McGuinty.

The provincial government has committed $600 million in funding for the project. The federal government has committed $200 million in funding, so far.

However, even if the federal government comes through to match Ontario's financial commitment, taxpayers in Ottawa will still be on the hook for about $300 million.