Leaders in the north of England fear that a new £39bn railway line could be scaled back, with the region ending up with a “cheap and nasty” alternative instead. The Greater Manchester mayor, Andy Burnham, and others are concerned that the government wants to water down plans to build Northern Powerhouse Rail (NPR), which is supposed to halve journey times in the region. Currently, travelling coast to coast by train in the north can take longer than getting from Leeds to Paris by rail. Burnham told a meeting on Thursday that the people of the north of England “will not forgive us” if their leaders did not fight against the region being palmed off with a “cut-price railway in the north and a fully funded railway everywhere else”. Sometimes described as “Crossrail for the north” – a nod to London’s vastly delayed, £18.7bn line – a properly funded NPR would be “the single most important infrastructure project in the north-west in the 21st century and potentially the most significant rail intervention in our region since the Rainhill trials, which led to the development of the world’s first passenger rail line between Liverpool and Manchester almost 200 years ago”, according to Steve Rotheram, the metro mayor of the Liverpool city region. Burnham said the leaders had a duty to ensure NPR was built in full, describing it as a decision that would “define the north of England for the rest of this century, and indeed, the one afterwards”. The business case for NPR was due to be signed off and published in March by Transport for the North (TfN), the statutory body set up to advise the government on the north’s transport needs. It would endorse a new line from Liverpool to Leeds via Warrington, Bradford and Manchester airport, and upgrades of lines to Sheffield, Hull and Newcastle. Leaders in the Liverpool city region are already concerned that government officials are trying to cut costs on their leg of NPR in what it calls the “minimum viable network”. In a letter sent to Grant Shapps, the transport secretary, on Thursday, Rotheram and others accuse him of favouring a “cheap and nasty” old route previously used to ferry coal to a power station, instead of investing in a new line. Using that route would go “nowhere near the original NPR vision of 20 minutes [travel time] between both [Liverpool and Manchester] cities”, the letter argues. At a meeting of the TfN board on Thursday, the leaders were told the government had asked for all discussions of the “preferred way forward for NPR” to be held in private, excluding the public and media. Last week the government wrote to TfN to ask it to delay publishing its NPR “strategic outline business case” until it had published its own “integrated rail plan”. The leaders worry this will allow the government to dismiss the most ambitious elements of NPR by saying they are incompatible with its national plan. “Our voice is being marginalised just at the critical moment, and our ambitions are being downgraded at the same time,” Burnham said. He added: “I think we’re in danger of being sidelined at the worst possible moment … It feels as though the [transport] department is slowly turning down the volume on TfN’s voice and most possibly getting ready to pull the plug.” Rotheram said the move was typical of the “recent and ongoing neutering of many of the things that we would like to do”. However, the leaders reluctantly agreed at the meeting that they had a “statutory duty” to do what the government wanted and delay the publishing of its NPR business case.