The troubled £42.6bn HS2 scheme – which promises 225mph trains from West Yorkshire to London – is an expensive leap in the dark, MPs warn today.

The Government has failed to “present a convincing strategic case” for high-speed rail as the cost of the project spirals, a powerful Commons committee has concluded.

And it is relying on “out-of-date data and assumptions which do not reflect real life” – exaggerating the benefits for businesses, by ignoring work done on trains.

The Public Accounts Committee (PAC) also warns that HS2 may end up “sucking even more activity into London”, rather than narrowing the North-South divide.

And the Department for Transport is accused of leaving it too late to ram through a complicated Bill, to secure planning powers, before the 2015 general election.

The criticisms are that latest in a series of attacks on the flagship project, which many Conservative – and some Labour – MPs are turning against.

However, all three political leaders are committed to building the HS2 network – providing the bill does not rise again beyond £50bn, including new trains.

Furthermore, rail experts have strongly backed the scheme as the best way to ease a capacity crunch on existing North-South lines, from the 2020s.

HS2 could also give Bradford – and other towns and cities – a direct rail link to London, transforming rail travel by freeing up space on those existing lines.

However, today’s PAC report demands:

  • Detailed evidence to show why HS2 is the best option for improving rail links between regional cities and “rebalancing the economy”.
  • A fresh business case, for phase two of HS2, based on “up to date information and realistic assumptions, particularly on the benefits to business travellers”.
  • Assurances that both legislation and building work can be completed on time.

Margaret Hodge, the PAC’s Labour chairman, said: “The Department for Transport has yet to present a convincing strategic case for High Speed 2.

“It has not yet demonstrated that this is the best way to spend £50bn on rail investment, in these constrained times, and that the improved connectivity will promote growth in the regions rather than sucking even more activity into London.”

HS2 is intended to deliver 225mph trains from London to Birmingham by 2026 – and a Y-shaped network, on to Leeds and Manchester, seven years later.