Labour peer Tony Berkeley has written to Chris Grayling, the transport secretary, warning that a "lack of detail" over the expense of the first phase of HS2 could mean it costs double what the Department for Transport (DfT) has estimated.
Berkeley, who has taken an active interest in the project, said there was a "lack of detail" on the costs of HS2 and that there had been a "marked unwillingness from ministers and officials to engage in discussions about costs". The project is currently estimated to cost £56bn, up from an initial cost of £32.7bn in 2010.
However, in his letter to Grayling on the costs of phase one - which will connect London to Birmingham - Berkeley said HS2 did not challenge estimations put forward by Michael Byng of the Stop HS2 campaign, whom he called an "acknowledged expert on railway costs".
Byng puts the costs of phase one at £51.25bn - double the DfT's estimate of £24bn and not far off the costs for the entire project.
Berkeley said DfT continued to estimate the costs of the first phase at £24bn, which he said the department could provide "no more detailed justification for".
"In the last year, there has been no official change given to the quoted £24bn for phase 1 and I have been unable to obtain any more detailed justification for this figure, and our contacts in the industry are expressing serious doubts about whether it is being built to this figure," Berkeley wrote.
HS2 Phase 1 costs now £51bn, due to increased scope, according to M Byng's new 4k+ page estimate. DfT still cling onto their £24bn, priced in 2013, but few in the sector believe them. DfT never challenged M Byng's methodology. Time to pause and descope. pic.twitter.com/ZYMPttDntF— tony berkeley (@tonyberkeley1) March 17, 2018
A DfT spokesperson said: “We do not recognise this cost estimate and are confident that HS2 phase one will not cost what they claim.
“We are keeping a tough grip on costs and the project is on time and on budget.”
The peer suggested that the project be paused to "enable Byng's figures to be verified" to avoid a "massive cost overrun".
“If there is a need for the project to be paused for a period to enable Michael Byng’s figures to be verified, surely this is worthwhile not only to confirm such a large amount of government funding, and also to avoid a massive cost overrun later?” he wrote.
HS2 has long attracted its critics, with the TaxPayers Alliance warning that costs could top £90bn if the high-speed rail project follows in the footsteps of other government-managed, large infrastructure projects.
The thinktank said taxpayers should "take no comfort" in government insistence that HS2 will be delivered on budget, given an "appalling track record".