The construction of HS2 - the high-speed railway set to cut through parts of Northamptonshire - should not go ahead unless its costs and benefits are reviewed,
That is the opinion of the House of Lords Economic Affairs Committee, whose members include former chancellors Lord Alistair Darling and Lord Norman Lamont.
The first phase of the controversial high-speed rail line was given Royal Assent in February 2017, and would see the railway between London and the Midlands pass through Northamptonshire between Brackley and Upper Boddington.
"We have serious reservations about the cost-benefit analysis used in determining whether High Speed 2 provides value for money," states the report.
"Cost-benefit analysis is an important discipline for comparing the merits of different projects.
"But it has serious limitations as a technique for examining the transformational benefits that new infrastructure can provide."
The committee concluded the construction should have started in the north of England where rail infrastructure is "required urgently", rather than in London.
The report also queried whether asking rail travellers questions about how much they would be willing to pay for quicker journeys was "the most robust evidence base" to calculate the benefits a multi-billion new railway would bring.
"New analysis of the project is needed which takes account of the transformative effects, including allowing for changes in land use, that new infrastructure can have," the report continued.
"The assumptions behind values of travel time and the demand forecasts should be revised ahead of this new analysis.
"This analysis should be published alongside the full business case by the end of 2019."
The Department for Transport described the Lords report as a “thorough assessment of a complex project” but said it “fundamentally disagreed with parts of it”.
"HS2 will generate around £92 billion in benefits to the UK economy, with local economic plans forecasting the creation of 500,000 jobs and nearly 90,000 new homes," said an HS2 Ltd spokesperson.
"Work is underway at over 250 locations and the scheme already supports more than 7,000 jobs directly and across our supply chain.
"As stated in the report, HS2 is fundamental to the delivery of Northern Powerhouse Rail.
"It is also vital to the Midlands Rail Hub, and will transform rail journeys across the Midlands and north, giving passengers thousands of extra seats every day, and taking freight off the roads.
"As regional leaders across the Midlands and north have repeatedly said, it’s not a case of either or, it’s both."