Campaigners hoping to convert a disused railway line into England’s longest cycle and pedestrian tunnel are challenging a government decision to fill much of the historic structure with concrete.

Earlier this month ministers decided to award several million pounds to permanently shutter the Queensbury tunnel built in the 1870s for a railway between Halifax and Keighley in West Yorkshire, despite spending £7.2m to shore up the structure less than four years ago.

The government has agreed to fund plans to infill the tunnel for safety reasons, by the roads agency, National Highways (NH), which is responsible for maintaining the historic railways estate.

The decision comes after the agency was widely criticised for “cultural vandalism” over the infilling of Victorian bridges on the railway estate. In 2023 it was forced to reverse burying in concrete a Victorian bridge in Great Musgrave, Cumbria, on the route of a scheme to join two heritage railway lines.

The mayor of West Yorkshire, Tracy Brabin, who backed calls to reopen the 1.4-mile tunnel which was closed to railway in 1956, has expressed disappointment at the government’s decision. In 2021, while standing at the entrance of the tunnel, she described plans for a subterranean cycle path linking Bradford and Keighley to Halifax as a “great facility for our community”.

Campaigners accused the government of “investing in destruction” and ignoring the views of 8,000 planning objections to the plan to infill the tunnel. They are due to meet Lilian Greenwood, the minister for the future of roads, next week to urge her to reverse the decision.

In a letter to campaigners, Greenwood said converting the tunnel for cycling would be too costly in “the challenging fiscal environment” and that “safety risks need to be addressed.”

NH’s contractors estimate it would cost £26.4m to convert the tunnel. But campaigners have dismissed this figure as “gold-plated” and claim the tunnel could be brought back into use as a greenway for only £13.7m – not much more than the £7.2m spent to shore it up from 2018 to 2021 including at least £3.9m now required to infill the structure.

They also point to a study by the charity Sustrans published earlier this year which found the proposed route would generate £3 in social, economic and tourism benefits for every £1 spent on it.

Norah McWilliam, the leader of the Queensbury Tunnel Society, said: “The government is making and investment in destruction to satisfy the needs of a roads body that only cares about its own narrow interests. Community aspirations to bring positive benefits from our fabulous historic asset mean nothing to these spreadsheet shufflers.”

She added: “These new millions and the seven lost in a black hole four years ago could have paid for the tunnel’s repair, safeguarding it for a role at the heart of an inspiring and sustainable active travel network – something Bradford and West Yorkshire could be proud of.”

Graeme Bickerdike, the engineering coordinator for the society, said: “The minister claims that her decision is based on a ‘full view of the facts’, but the evidence seems to have come exclusively from National Highways which has a proven track record for exaggerating risk, misrepresenting condition evidence and frittering away public funds.

“There is no justification for another costly tunnel intervention at this time as the 2018-21 works have reduced what was already a low risk profile.”

Brabin said she shared the disappointment of campaigners, but said she understood the government’s decision. She said: “To ensure everyone’s safety the government had to act quickly to secure the site, and the realities of public finances meant a difficult decision needed to be made.

“We remain committed to helping support alternative routes for walking, wheeling and cycling between Bradford and Calderdale.”

A Department for Transport spokesperson said: “Given the continued deterioration of the Queensbury tunnel, and in the absence of local funding to develop it as a transport link, National Highways has been instructed to carry out works to maintain public safety.

“This has been a difficult decision but ultimately, we have a responsibility to safety and delivering value for the taxpayer.”