The government has been asked to intervene to cease work on the abandoned Queensbury Tunnel in Bradford.
The ongoing work carried out by Highways England to fill in and seal an air shaft in the tunnel could stop plans for the development of what would become Europe's longest underground cycleway.
The 1.4 mile abandoned railway tunnel dates back to the Victorian era, and its conversion into a cycle track between Bradford and Halifax has been hailed as a “once in a lifetime opportunity” to preserve what could become a major attraction to the region.
Last week, Highways England's contractor moved on to the site and began filling in one of its air shafts, with the government owned company stating that "any reopening is now going to be more challenging" as a result of their work.
Bradford Council has revealed the current planning application to fill and seal the tunnel has received more than 4,000 objections, and Susan Hinchcliffe - the leader of Bradford Council leader - has asked Grant Shapps MP to help stop work on the tunnel.
In the letter, she wrote: "We have a once in a lifetime opportunity to save this unique asset of our Victorian industrial heritage and restore it as part of a nationally recognised cycleway that will become a national visitor attraction in its own right."