Campaigners have warned the government that any move to scrap high-speed rail network HS2’s route towards Leeds will “make a mockery” of its pledges to empower the north.

The project is at risk of being scaled back after spiralling costs and delays look set to see the network completed as much as seven years late and more than £20bn over budget.

However, local politicians have responded with anger to claims in the Financial Times that the panel reviewing the infrastructure project was considering axing the route from the East Midlands to Sheffield and Leeds.

Under the proposal the route, one of two forks of the northern track due to make up phase two of the building project, would be cut short to Toton, a new hub station between Nottingham and Derby.

The second prong of the track would then continue on to Crewe, Manchester and Wigan as originally planned, it was reported.

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“If this story is true it will remove the part of HS2 with greatest economic impact, making a mockery of rhetoric of ‘Northern Powerhouse’”, Leeds City Council chief executive Tom Riordan said on Twitter, referencing the commitments of Mr Johnson and George Osborne before him. “Given the time, energy & money wasted, how can people who’ve worked on this in good faith for years ever trust a national process again?”

Labour MP Lillian Greenwood said that she hoped the claim was wrong, calling the potential move “a complete and utter betrayal of the Midlands & the North” and adding that regional politicians would “fight it every step of the way”.

Her colleague Hilary Benn meanwhile warned the government that “we will not accept HS2 to Leeds being cancelled”. He added “The north has been denied its fair share of transport investment for too long.”

The infrastructure project has been controversial since it was proposed by Labour in 2009 – facing opposition by both those concerned by its monumental cost and those who feared its impact on nature. Wildlife campaigners have warned that dozens of areas of “irreplaceable” ancient woodland will be destroyed by the scheme.

The project has also suffered significant delays and rising costs. In September, HS2 Ltd chairman Allan Cook admitted that the original plans “did not take sufficient account” of the difficulty posed by building a high-speed line through densely populated areas with challenging ground conditions.

However, despite these issues HS2 has held widespread support among officials in the north who have long bemoaned the state of the region’s transport links.

Judith Blake, the leader of Leeds City Council and transport lead for the West Yorkshire Combined Authority, said there would be “grave long-term consequences” for the economy in the north and east of the country if HS2 was not delivered in full.

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She added: “It would sacrifice the £600m of annual GDP growth forecast from better connections between Leeds and Birmingham alone, while also putting at risk the expected 50,000 additional jobs HS2 would create in the Leeds city region.

“The lack of additional capacity provided by HS2 would put further pressure on an existing network which is already struggling to cope with demand, with 8 per cent of East Coast Main Line intercity services already cancelled or significantly late and Leeds station the third busiest outside of London – and the fourth worst in the country for overcrowding at peak times.

“With trains between Leeds and Sheffield currently travelling at an average speed of 36mph, failure to deliver HS2 in full to Leeds while going ahead with a western leg providing services travelling at 250mph would condemn the North and East of the UK to second-class status.”

A Department for Transport spokesperson said: ““The secretary of state has established an independent review into HS2 which will provide the department with clear advice on how and whether the project should proceed. We are not going to pre-empt or prejudice this work with a running commentary on the review’s progress.”