Failing to build HS2 in full would be a “betrayal” of Northern voters, Boris Johnson is warned tonight.

Regional leaders fear the Prime Minister is poised to axe the eastern leg of the 225mph rail project to cut costs.

Insiders believe the Integrated Rail Plan, which will decide whether the full scheme goes ahead, will be published within weeks.

In a letter to the PM, seen exclusively by the Mirror, Northern chiefs say that stalling over extending the scheme towards Nottingham, Sheffield and Leeds costs nearly £5billion a year.

The letter, signed by Sheffield City Region Metro Mayor Dan Jarvis, Leeds City Council leader Judith Blake and Notts County Council boss Kay Cutts, says: “Levelling up is an ambitious objective and one that can make a real difference to the economies of the North and Midlands, as well as the quality of life and employment opportunities for people who live there.

Sheffield City Region Metro Mayor Dan Jarvis

“The commitment to deliver the Northern parts of HS2 in full is the first test of the reality of the levelling up agenda.

“Going back on this commitment would see levelling up fall at the first hurdle, and would make a vision of a balanced, fair country for everyone impossible to deliver.”

Further doubt was cast on the high speed rail link for major parts of the North last month(DEC) after experts called for other projects to get priority.

The National Infrastructure Commission said investment should be pumped into regional networks rather than building the full HS2 line to Leeds.

The line is due to serve Leeds, as well as Birmingham and Manchester

The NIC's Rail Needs Assessment claimed it would be "potentially cheaper and faster" to deliver improvements to regional journeys through a combination of new lines and upgrades, rather than Phase 2b of HS2.

Plans involve Phase 1 running from London to Birmingham, Phase 2a from Birmingham to Crewe, and Phase 2b from Crewe to Manchester, and from Birmingham to Leeds.

Ms Blake said tonight: “Local leaders, MPs and businesses from right across the East Midlands, Yorkshire and the North East are crystal clear – the eastern leg of HS2 must go ahead in full.

“Anything less would be a complete betrayal by the Government, given the repeated commitments they’ve made to deliver HS2 in full.

“We’re talking about a failure to create 150,000 jobs, and transform the economies of parts of the country that have suffered huge decline over many decades.

Trains will run at 225mph
Leeds City Council leader Judith Blake

“The uncertainty is deeply damaging for all of our regions.

“Every year of delay costs the whole eastern leg regions £4.9billion and Leeds City Region £1.7bn alone.

“Far from scaling HS2 back, the Government could show a genuine commitment to levelling up by starting the build from Leeds – getting spades in the ground, creating jobs and giving businesses the confidence to invest in the genuinely transformational projects our city region has planned.”

Newcastle-upon-Tyne MP Catherine McKinnell said: “The North East stands to benefit from HS2 as much as any of the towns and cities on the route.

“The opportunity to better connect Newcastle to Leeds, the Midlands and the South would be a huge boost to our region, and help to provide the extra capacity on our railways we so badly need.

Newcastle MP Catherine McKinnell

“That the Government is even contemplating cutting the eastern leg shows how little they value this part of the country.

“Voters will not forgive or forget any attempt to short change the North.

“It’s the same old story – London and the South get what they want while the North is left with second best.”

A Government spokeswoman said: “We’re committed to bringing the benefits of high speed rail to the East Midlands, Yorkshire and beyond.

“Our Integrated Rail Plan will outline how projects, including HS2 and Northern Powerhouse Rail, can work together to deliver the reliable train services that passengers need and deserve, as quickly as possible.”