The budget for the High Speed 2 railway has increased by nearly £10 billion to more than £40 billion, the Transport Secretary has told MPs.
Ahead of an expected rebellion by Conservative MPs, Patrick McLoughlin said the £42.6 billion budget included a large contingency fund.
The original budget had been about £33 billion.
The new High Speed 2 (HS2) line is set to link London to Birmingham by 2026. Two second-phase branches to Manchester and Leeds, via Sheffield, are planned by 2032.