Northern leaders have called on Downing Street to honour promises to build the HS2 high-speed rail line, as ministers repeatedly refused to confirm to MPs whether it would run to Manchester.

Doubts over the future of the multibillion-pound HS2 project are growing after the junior transport minister Richard Holden dodged multiple questions in the Commons.

Reports at the weekend said the prime minister, Rishi Sunak, was set on cutting HS2 short after the initial phase to Birmingham.

The Greater Manchester mayor, Andy Burnham, said the reports “beggared belief” after the promises of successive Conservative governments over the past 10 years.

Labour said it was “committed to delivering HS2 in full and maximising its economic benefits”, after doubts were raised over its own policy.

The shadow transport secretary, Louise Haigh, said HS2 would provide a slower journey between London and Birmingham than current train services if the project is cut back.

Originally planned as a Y-shaped route between London and the north, HS2 has been cut back repeatedly amid ballooning costs, with the eastern leg to Leeds scrapped in 2021 and the Manchester leg delayed by another two years in March.

The upper range of official costs are now put at about £71bn, in 2019 prices, excluding the unspecified northern leg which could cost £8bn. However, costs are believed to have risen substantially since then due to high inflation. Lord Tony Berkeley, the vice-chair of the Oakervee review of HS2 commissioned by Boris Johnson and a Labour peer, claimed that estimated costs of the high-speed rail scheme were now about £180bn.

Haigh said: “Here we are yet again. 13 years of gross mismanagement and chaos coming home to roost. First they slashed Northern Powerhouse Rail, then they binned HS2 to Leeds, then they announced the line would terminate at Old Oak Common for years to come, and now it looks like they are considering cutting the north of England out in its entirety.”

Holden repeatedly stated that “spades are in the ground” when asked to confirm that the Birmingham to Manchester line had a future, and instead attacked Labour’s “£140bn uncosted commitments” to build HS2 and Northern Powerhouse Rail in full.

Speaking to the Guardian, Burnham urged Sunak to end the uncertainty and consult people in the north. He said no northern leaders had been consulted about changes that apparently had been briefed, including re-announcing a modified east-west line.

He said: “I don’t consider that to be fair or acceptable to mayors or the public.

“It’s a decade since George Osborne came here and promised us the earth – HS2, HS3, better TransPennine services – and none of that has happened, it’s gone backwards. No wonder people are cynical about politics.

“Why does the north of England have to choose between a good east-west line and north-south? London has both.

“If the briefings are to believed … the south-east linking up to the Midlands with high-speed trains, while the north struggles on with Victorian infrastructure, nothing would illustrate the inequality clearer than that.”

Holden, standing in for the transport secretary, Mark Harper, and the rail minister, Huw Merriman, came under pressure from his own backbenches, with Tory MPs questioning the logic of the entire project if it does not go to Manchester.

Iain Stewart, the Conservative MP who chairs the transport select committee, referred to reports of plans to potentially end the line early in Old Oak Common in north-west London – instead of running into Euston – as part of a cost-cutting exercise.

“If what has been reported is true, it would be an enormous false economy. Whether you support or oppose in principle, starting from Old Oak Common will not realise the full potential of the project and will have come as an enormous cost to communities,” he added.

Robert Syms, another Tory MP and a member of the same committee until recently, said: “The logic of the project is that it does have to go to Manchester and beyond. Otherwise it wasn’t worth starting.”

The fate of the HS2 network was thrown into doubt last week as Downing Street confirmed discussions about possible spending cuts before the November autumn statement, and refused to confirm the line would go to Manchester.

A senior government source since quoted in the Times claimed Sunak had “made up his mind” to scrap the Manchester HS2 link and the line running into Euston in central London, stopping instead at a new Old Oak Common station six miles west.

The reports come just six months after ministers announced that construction would be paused in places, and high-speed services to Manchester would not start until almost a decade later than originally promised.

HS2 Ltd has so far spent around £585m on buying up 954 properties and land for the second phase, which is now in doubt.

A Labour frontbencher, Nick Thomas-Symonds, said on Monday evening the party would build HS2 and Northern Powerhouse Rail – the term used for projects to connect northern English cities – “in full”. “That’s the clear pledge that we have given,” he said.

Pressed by the BBC on what he meant by “in full” and whether this included plans not just to go to Manchester but also to Leeds, he said: “It’s both to Manchester and indeed the eastern leg you have referred to.”

Burnham, speaking as Manchester launched its Bee Network app before franchised bus services come back under public control, said the city was making “a major change to public transport that we believe will bring massive improvement – but on a national level it’s going backwards”.

The West Yorkshire mayor, Tracy Brabin, said the government seemed “determined to deliver the fatal blow for HS2 in the north”, having already axed the direct line to Leeds with the status of the remaining north-eastern leg under review. She added: “We are crying out for our fair share of transport investment to help us build a better-connected region – but once again the north is just an afterthought for this government.”

Berkeley criticised the public accounts committee and the National Audit Office for accepting Department for Transport cost estimates. He said Sunak would be right to end the line into London at Old Oak Common, which he said could save £12bn, adding that it was “time to start again from scratch” north of Birmingham.

Merriman was later revealed to be in the Czech Republic signing a declaration of cooperation on high-speed rail.