THE future of HS2 is in doubt after the UK Government announced a fundamental review of the controversial £56 billion project but one union chief suggested it provided a “golden opportunity” to extend the scheme to Scotland.

Some £7.4 billion has already been spent on, among other things, buying up properties and landscaping.

Grant Shapps, the Transport Secretary, said the review would be “rigorous” and stressed how the Government needed “clear evidence” before proceeding with the major infrastructure project.

“Just give us the facts,” declared Mr Shapps. “Then we will know and we will be in a much better position to make the decision to go or no go by the end of the year.”

Boris Johnson first raised his desire to reappraise HS2 during the Conservative leadership campaign in June. At the time, he suggested, if he won the contest and became Prime Minister, his government would “look at the business case” and “think about whether and how we proceed”.

Douglas Oakervee, the former Chairman of HS2 Ltd, who has previously said it would be “catastrophic” if HS2 were cancelled, will lead the review. But his deputy, Lord Berkeley, is a long-term critic of the high-speed railway scheme.

The Department for Transport said the review would use all existing evidence on the project to consider: its benefits and impacts; affordability and efficiency; deliverability and scope; and phasing, including its relationship with Northern Powerhouse Rail.

It will consider the potential for cost reductions by changing the scope of the project covering such things as:

*reducing the speed of the trains;

*making Old Oak Common the London terminus "at least for a period" instead of Euston;

*building only Phase 1 between London and Birmingham;

*combining Phase 2a - extending the line to Crewe - with Phase 1 and

*altering plans for Phase 2b, which currently involves taking the line to Manchester and Leeds.

Manuel Cortes, General Secretary of the TSSA rail union, said the Government was “going down the wrong track with this review” and argued it should first and foremost be considering the vast economic, social and environmental benefits of HS2 to the whole country.

“This is a golden opportunity – using a clean and green scheme - to put rocket boosters under regional economies across the country, create thousands of additional jobs and better connect cities.”

He added: “We need HS2 to run the length of Britain - from London to Scotland - delivering 21st century transport links which will reboot our economy beyond the south east."

In July, Allan Cook, the HS2 Chairman, wrote to the department, stressing how the high-speed line could not be delivered within its £56bn budget; he suggested another £30bn might be needed.

HS2 would connect London, the Midlands and northern England using trains capable of travelling at 250mph.

The first part of the major infrastructure project between London and Birmingham is due to open at the end of 2026 with the second part to Leeds and Manchester expected to be completed by 2033.

HS2 will cut journey times significantly: from Birmingham to London from one hour and 21 minutes to 49 minutes; from Manchester to London from two hours and eight minutes to one hour and eight minutes; and from Glasgow and Edinburgh to London from four hours and 30 minutes to three hours and 30 minutes.