Euston station will not be the terminus for HS2 unless enough private investment is secured.

According to the PA news agency, Rishi Sunak’s commitment to extend the high-speed railway to the station is contingent on a substantial proportion of the cost being met by private funds.

If not enough money is found, HS2 will permanently stop at Old Oak Common in west London.

Extending HS2 to Euston involves digging a 4.5-mile tunnel from Old Oak Common and building a six-platform station next to the existing West Coast Main Line terminus.

At his speech to the Conservative Party conference on Wednesday (October 4), the Prime Minister said: “We will complete the line from Birmingham to Euston.”

He added that the Government’s new plan for the central London station will generate “£6.5 billion of savings”.

A No 10 source said the figure was a combination of replanning the project after considering “what is no longer required” and a developer contribution model such as the one used in Battersea, south-west London.

DfT officials believe the capacity of Old Oak Common as a terminus station can be stretched to eight trains per hour, which is the same as planned for Euston after the scrapping of HS2 north of Birmingham.

But there are concerns at the comparative lack of options for onward journeys from Old Oak Common.

Government modelling shows two-thirds of people would prefer to travel to or from Euston.

HS2 work at Euston was paused in February because costs had ballooned to £4.8 billion compared with an initial budget of £2.6 billion.

The DfT said it will appoint a development company, separate from HS2 Ltd, to manage the delivery of the Euston project.

Euston was initially due to have 11 platforms for high-speed trains but will now have six.

Railway consultant William Barter, whose recent clients include the DfT, told PA the plan was “totally unambitious” as it “rules out options” for expanding the railway north of Birmingham in the future.

A Government spokesperson said: “As we have always planned, the new line will finish at Euston – that has not changed.

“It is simply wrong to talk down the scale and benefits of this regeneration. The new plan for Euston represents a world class regeneration opportunity, and the strengths of this approach are evidenced by recent developments at Battersea and nearby King’s Cross.

“There is already support and interest from the private sector. Ministers have had discussions with key partners since the announcement and the Transport Secretary will be meeting with the Euston Partnership in the coming weeks.”

Reporting by PA.