High Speed 2 could now cost an eye-watering £106billion, according to a leaked draft report - which despite everything says the train line should still go ahead.

The shock review, handed to the Financial Times, warns there is a "considerable risk" the price could spiral by 20% on top of an estimate of £81bn to £88bn.

That would put it at almost double the official cost of £56bn.

Doug Oakervee, the independent expert who Boris Johnson told to review the project, is said to have recommended a six-month "pause".

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That would give officials time to see if the line could be built with a mix of conventional and high-speed track to cut costs.

But the leaked review says that "on balance", the line from London to Birmingham, Manchester and Leeds should go ahead and would cost £3.6bn to cancel.

A Whitehall source stressed the leaked review was only a draft and Transport Secretary Grant Shapps asked for more work to be done last week.

(Image: PA)

A Department for Transport spokesman said: "A draft of the Oakervee Report was delivered shortly before Christmas.

"The Transport Secretary, Chancellor and Prime Minister will take a final decision on HS2 shortly."

The first phase of HS2 to Birmingham was due to open in 2026 with Manchester and Leeds extensions in 2033.

But the report seen by the Financial Times says it would only be finished by 2040.

Some new Tory MPs want Boris Johnson to scrap the line, which cuts through heartland constituencies between London and the Midlands.

(Image: Department for Transport)

New MP Andy Carter told the BBC's Westminster Hour: "We need to look very carefully at whether this is the right project and whether it’s going to actually achieve what we want it to achieve.

"Getting from Manchester to Leeds, getting from Warrington to Liverpool, is a priority for people that live in the north of England.

"And I suspect that priority is well ahead of getting down to London or for people coming up from London."

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But city leaders have piled pressure on the Prime Minister to sign off the flagship high-speed rail project.

Northern Powerhouse Partnership director Henri Murison said: "This is a seminal moment in the modern history of the UK.

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"Any failure to seize this opportunity would be a betrayal of the North, and the promise of a Northern Powerhouse."

Manuel Cortes, TSSA union General Secretary, said: “The dithering and speculation over HS2 needs to stop. This vital infrastructure project is overdue and both business and communities are suffering in its absence."

(Image: WPA Pool)

West Midlands mayor Andy Street, Greater Manchester’s Andy Burnham and Leeds council leader Judith Blake warned the Prime Minister that voters would be “watching and waiting”.

They wrote in the Sunday Times: “People in the part of the Midlands and the north have handed Boris the keys to Downing Street.

"Now he must unleash the potential of our regions. High-speed rail is the place to start.”

Boris Johnson guessed last summer that the cost of HS2 would "probably be north of £100bn" but admitted he would "hesitate for a long time" before scrapping it.