The next government must make a fresh case for spending £50bn on High Speed 2, an influential Parliamentary committee said last week.
The cross-party House of Lords economic affairs select committee said evidence put forward to justify the project was unconvincing.
Plans for the rapid rail link are well advanced, with project promoter HS2 Ltd launching procurement processes for about £1bn of engineering, design and oversight work earlier this month.
But in its report the committee said more work should be done before the Hybrid Bill to allow phase one work to begin is passed.
“The cost-benefit analysis for High Speed 2 (HS2) relies on evidence that is out-of-date and unconvincing,” says the report.
“The Government needs to provide fresh, compelling evidence that HS2 will deliver the benefits it claims,” says the report.
“The government is basing the justification for HS2 on two factors - increased rail capacity and rebalancing the UK economy; we have not seen the evidence that it is the best way to deliver either,” said the committee’s chairman Lord Hollick.
A Department for Transport spokesman said: “The case for HS2 is crystal clear. It will have a transformational effect, supporting growth in the North by improving connectivity; freeing up space on our crowded rail network; promoting regeneration; boosting local skills; generating tens of thousands of jobs; and helping secure the UK’s future prosperity.”