THE UK Government’s review of HS2 is a “golden opportunity” to consider extending the £56 billion project to Glasgow and Edinburgh, a trade union chief has insisted.

The Department for Transport has today announced the timetable and terms of reference for Boris Johnson’s promised “independent and rigorous” review of the controversial high-speed rail project.

While the Government move confirmed the possibility that the major infrastructure project could be scrapped, saying the review would consider "whether and how HS2 should proceed," Manuel Cortes, General Secretary of the railways’ TSSA union, said it provided a clear chance for UK ministers to consider extending HS2 to Scotland.

“The Government is going down the wrong track with this review,” declared Mr Cortes, saying it should first and foremost consider the vast economic, social and environmental benefits HS2 could bring 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.

“HS2 is an essential pillar of our country's modernisation and will be vital in assisting local authorities and business in the rebalancing of Britain’s economy.

“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," he added.

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The department explained that the review, to be conducted by Douglas Oakervee, the former Chairman of HS2 Ltd, 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.

A final report will be sent to Grant Shapps, the Transport Secretary, with "oversight from the Prime Minister and Chancellor of the Exchequer" by the autumn.

"The Prime Minister has been clear that transport infrastructure has the potential to drive economic growth, redistribute opportunity and support towns and cities across the UK but that investments must be subject to continuous assessment of their costs and benefits,” said Mr Shapps.

"That's why we are undertaking this independent and rigorous review of HS2.

"Douglas Oakervee and his expert panel will consider all the evidence available and provide the department with clear advice on the future of the project," he added.

Mr 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 PM, Mr Oakervee would be hired to “have a look at the business case” for the project and “think about whether and how we proceed”.

Although Mr Oakervee has previously said it would be “catastrophic for the UK” if HS2 were cancelled, the very fact Mr Johnson has ordered a review raises doubts about whether or not the project will ever be realised.

He was said to have told a private meeting of Conservative chairmen that while he was “worried” about the idea of cancelling such a big national project, he suggested the spending could be “reprofiled” to prioritise railway improvements in northern England.

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.

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HS2 would connect London, the Midlands and northern England using trains capable of travelling at 250mph. But, of course, it would reduce journey times across the whole of Britain, cutting an hour’s journey time from Glasgow and Edinburgh to London.

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; from Leeds to Birmingham from two hours to 57 minutes and from Glasgow and Edinburgh to London from four hours and 30 minutes to three hours and 30 minutes.