Phase one of a the HS2 rail link between London and Birmingham has been delayed by up to five years by the British government.
With attention diverted by the ongoing Brexit drama, transport minister Grant Shapps revealed it could now be between 2028 and 2031 before the first trains run on the route.
Initial plans had called for the service to open by 2026.
Schapps said the cost of the project had spiralled to as much as £88 billion, up from estimated of £62 billion.
The second phase has also been delayed.
The route - from Birmingham to Manchester and Leeds - was due to open in 2032-33, but that has been pushed back to 2035-2040.
Shapps’ statement was based on a report from the chairman of HS2, Allan Cook, which concluded that the new railway could not be delivered within the current budget.
“I want the house to have the full picture.
“There is no future in obscuring the true costs of a large infrastructure project - as well as the potential benefits,” said Shapps.
Cook said the delay had occurred because the original plans did not account for the effect of building through densely-populated areas with difficult geographical features.
His report comes ahead of a government decision on whether HS2 will go ahead at all.
Last month, the government said it planned to review the costs and benefits of the rail project, with a “go or no-go” decision by the end of the year.
The government has said that construction work will continue while the review is ongoing.