LONDON — UK Transport Secretary Heidi Alexander announced that the HS2 high-speed railway will now cost up to £102.7 billion, with the first trains between Old Oak Common in west London and Birmingham Curzon Street running between 2036 and 2039. The full route from London Euston to a junction with the West Coast main line in Staffordshire is scheduled for completion between 2040 and 2043.

The total cost is estimated to range between £87.7 billion and £102.7 billion, with only a third of the rise owing to inflation, Alexander said. She said two-thirds of the budget increase was due to works missed from the scope of the original plans, under-estimates and inefficient delivery. The £102.7 billion figure is the first official estimate of the project's budget in 2026 prices.

Alexander said the government had considered cancelling the entire project, but said it could cost almost as much to cancel the line as finish it. She promised: "We will deliver HS2 to completion." She said Wild and HS2 Ltd's chair Mark Brown would have an almost impossible task to turn the project around but would be managing contracts properly with improved oversight.

"I can confirm that the previous government spent most of HS2's budget without laying a single mile of track. That is the shocking legacy," Alexander said. She added: "If it seems like an obscene increase in times and costs, that is because it is. And if it seems like I'm angry, I am."

Trains will be operated at lower speeds to save about £2.5 billion by reducing the top speed from about 225 mph (360 km/h) to about 200 mph (320 km/h). The change reduces the cost and time needed for testing new trains and cuts the specifications of the control and signalling system. Plans to build the line with automatic train operation are expected to be dropped.

"I recognise this will be unwelcome news for local communities and taxpayers, and I share in their disappointment that it will take longer and cost more to bring HS2 into service," said Mark Wild, chief executive of HS2 Ltd. Wild added: "Resetting HS2 was the only way to regain control of the project. We have turned a corner in the last 12 months with significantly improved levels of productivity, helping us to deliver major milestones ahead of schedule. Better journeys, more capacity on the network, and economic growth are all vital to the country's future prosperity, and that's exactly what we will deliver."

The HS2 project was first approved in January 2012 with a £32.7 billion budget to build a Y-shaped high-speed track as far as Manchester and Leeds, scheduled to be in operation by 2026. The original budget excluded rolling stock, which is now included in the revised figure. The range in the new budget, which excludes future inflation, is partly due to continued uncertainty over the size and shape of London Euston. The government hopes to partly privately finance the Euston works, and spending on HS2 is guaranteed until 2029–30 under the spending review. High-speed services will run to Manchester and Scotland at slower speeds using conventional lines once the HS2 line is connected to the main line at Handsacre in the early 2040s.