OTTAWA -- An internal government memo claimed last fall that the federal Liberals' decision to ditch plans to install tolls on a major new Montreal bridge could knock as much as $301 million off the final construction price.

But a spokesman for Infrastructure Minister Amarjeet Sohi would only say Friday that the change of plans won't raise the $4.23 billion price tag to replace the federally owned Champlain Bridge.

The Liberals' 2015 election platform called for a toll-free replacement bridge, which is a key link to the city for some 50 million vehicles per year and one of Canada's busiest spans.

The project became a source of controversy in recent years after the previous Conservative government announced the new structure would feature tolls, unlike the existing bridge.

The Trudeau government's move to reverse the Tory decision was pitched internally as producing a discount -- at least up front.

A "secret" December briefing note for Sohi said Ottawa's private partner in the project had been instructed to stop tolling-related work.

"While the savings from not implementing tolls have been estimated at up to $301 million, the amount will not be finalized until negotiations with the private partner are concluded, which could take up to 18 months," said the memo.

The document, obtained by The Canadian Press under the Access to Information Act, did not say how much revenue could be generated if tolls were installed on the bridge.

The note was prepared ahead of Sohi's Dec. 14 meeting with officials from the Privy Council Office and the Prime Minister's Office.

On Friday, Sohi held an event at one of the construction sites for the new bridge to mark the first anniversary of the project, which is scheduled for completion by the end of 2018.

The internal document said his department intended to "maximize savings" achieved by scrapping the toll elements in the project, which is a public-private partnership.

"We have been in discussions with Signature on the Saint Lawrence Group regarding the financial details and therefore are not in a position at this time to provide information on expected savings or estimates," Brook Simpson, a spokesman for Sohi, said in an email Friday.

"We can however confirm that the cost of the project will not increase as a result of the government's decision not to charge a toll."

The Liberals don't appear to be opposed to all forms of tolls.

The Trudeau government has shown an openness to user-pay systems as it considers infrastructure investment models that would engage institutional investors, such as pension funds, to help raise money for public projects.

Senior pension plan officials have said they would invest in public infrastructure projects as long as there are reliable, predictable returns, which could include user fees such as road tolls.

In defending the Liberals' decision on the new Champlain Bridge, Sohi has insisted the structure shouldn't have tolls because the existing one doesn't have them.

In contrast, Sohi has noted that the Confederation Bridge, which connects Prince Edward Island to the mainland, has had a toll since it first opened.

After announcing his government would replace the crumbling Champlain Bridge several years ago, then-prime minister Stephen Harper faced intense pressure in the Montreal area and Quebec to get rid of its proposed toll system.

But Harper stood firmly by his decision, arguing it was a bridge for the Montreal region and that locals should help finance the project since it was unique in Canada.

Nova Scotia Sen. Michael McDonald has said Ottawa should have tolls on all its bridges to ensure equal treatment of users in all parts of the country.