Prime Minister Mark Carney's already eye-wateringly expensive high-speed rail project could become even more costly after the federal government ordered planners to add a stop in Kingston.

The Canadian Taxpayers Federation (CTF) estimates the additional stop would add $3.9 billion to the project's construction cost, while increasing long-term operating subsidies by another $2.8 billion.

"This project was already unaffordable for taxpayers with a $90-billion price tag and now it will cost billions more because the Carney government is adding an extra stop," said Noah Jarvis, the CTF's Ontario director. "The project hasn't even started and it's already obvious there will be huge budget overruns."

The Carney government's high-speed rail project is already veering off the rails.

The transport minister wants to add an Alto stop in Kingston.

We estimate it'll cost taxpayers an extra $3.9 billion to add Kingston to the Alto route.

And the rule for big high-speed rail… pic.twitter.com/1xb42KAdgB

— Noah Jarvis (@noahrjarvis) July 8, 2026

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Transport Minister Steven MacKinnon recently directed Alto, the Crown corporation overseeing the project, to develop plans that include a stop in Kingston. According to the CTF, that would require extending the rail line by at least 51.9 kilometres.

Using the midpoint of the federal government's own estimated construction cost—between $60 billion and $90 billion, or roughly $75 million per kilometre—the CTF calculates the Kingston extension alone would increase construction costs by approximately $3.9 billion.

The taxpayer watchdog also projects the additional stop would increase operating subsidies by $2.8 billion over the life of the project. That estimate is based on research from McGill University, which concluded the original high-speed rail proposal would require $53.1 billion in taxpayer subsidies over 43 years.

The CTF argues the Kingston addition is another example of "scope creep"—a well-known driver of cost overruns on major infrastructure projects.

Research by megaproject expert Bent Flyvbjerg found the average rail megaproject exceeds its original budget by 39 per cent. International examples include California's high-speed rail project, where design changes have added an estimated US$5.5 billion in costs, and Britain's HS2 project, whose escalating price tag has also been attributed in part to repeated scope changes.

"The government's $90-billion cost estimate isn't realistic," Jarvis said. "Taxpayers can't afford this boondoggle and it needs to be scrapped."