Prime Minister Theresa May has pledged that the whole of the HS2 high speed rail network will be built, including services to the North.

And she said that the project would be adapted to ensure it fits in with plans for a new line connecting the north east with the north west, known as Northern Powerhouse rail.

It follows reports that the Government could cancel HS2, the planned new rail line connecting London, Birmingham, Leeds and Manchester.

There have also been reports that the Government is considering pressing ahead with with phase one, between London and Birmingham, but scrapping phase two, which extends the line to the north of England.

In a letter to local government and business leaders in Birmingham, Manchester, Leeds and Liverpool, Mrs May said: "I would like to take this opportunity to assure you that the Government remains committed to delivering the whole of HS2 Phase 2 and will continue to work closely with you to ensure that the project meets your aspirations for growth and regeneration."

She said the Government could make changes to the proposed route so that it allows Northern Powerhouse Rail, and possible improvements to links between the West Midlands and East Midlands, to go ahead.

Mrs May said: "The Government recognises the benefits of a fully integrated rail network and, for this reason, it is essential that any changes support Northern Powerhouse Rail and Midlands Connect."

A March 2012 view towards Curzon Street Railway Station, showing the depth of concrete at the future HS2 site
A March 2012 view towards Curzon Street Railway Station, showing the depth of concrete at the future HS2 site

The Prime Minister was responding to a letter from a number of business and political leaders in the North and Midlands, who had urged the Government to finish HS2 "in full", saying it would create "hundreds of thousands more new jobs".

Those signing the letter included Judith Blake, Leader of Leeds City Council; Charlie Cornish, Group Chief Executive of Manchester Airports Group; Steve Rotheram, Mayor of Liverpool City Region; Ian Ward, Leader of Birmingham City Council, and Professor Dame Nancy Rothwell, Vice-Chancellor of The University of Manchester.

Her comments were welcomed by Sir John Peace, Chairman of Midlands Connect and the Midlands Engine.

He said: "The government has sent the Midlands and the north a strong, positive message: HS2 is happening, it’s already a huge catalyst for growth, and it supports major upgrades to the existing rail network through the work of Midlands Connect and Northern Powerhouse Rail.

"During a crucial transitional period for the country, and with the comprehensive spending review due this autumn, it is our responsibility as business and civic leaders to keep making the case for HS2.

"It is essential to the economic futures of the Midlands and the North, and we are building our growth plans around it. Now is not the time to falter."

Some opponents of HS2 claim that scrapping it would allow improvements to rail services in the North of England to go ahead.

However, the Northern Powerhouse Rail project, drawn up by a transport authority called Transport for the North, involves adding a new line between the North East and North West which would connect directly into HS2.

CGI of plans for the new HS2 station in Curzon Street, Birmingham
CGI of plans for the new HS2 station in Curzon Street, Birmingham

The first phase of HS2 is due to open in December 2026. Trains will travel at high speed between London and Birmingham, with new stations in Birmingham city centre and near Birmingham Airport.

Phase 2 turns the line into a "Y" shape, taking it in two directions from Birmingham to the north east and north west of England. A route to Leeds and York will run east of Sheffield. The western route will see trains pass from Crewe to Manchester.

Ministers say the line will be finished by around 2032 and 2033.

Critics include think tank the New Economics Foundation, which published a report suggesting HS2 should scrapped and the money used to help improve rail services in less well-off areas.

It suggested spending £55.2billion over the next 10 years, including £18.9bn for the north, on the full electrification of much of the northern rail network, as well as the Midland and Great Western lines.

The report also calls for the reopening of the trans-Pennine Woodhead line between Manchester and Sheffield, a Bradford crossrail to connect the two lines that terminate in the city, and the creation of more four-track sections on the north-south mainlines.