CAMPAIGNERS fear design changes to a proposed new 35-mile rail route linking Edinburgh with the Borders could lead to journey times being extended from 55 minutes to more than an hour, making it far less appealing to commuters.

The Campaign for Borders Rail (CBR) says a new railway connecting the capital and Tweedbank could be the "slowest in east-central Scotland" if cuts to the £295 million project are implemented.

The claims have been rejected as "inaccurate" by Transport Scotland, the Government agency overseeing the project, which will reconnect the Borders to the UK rail network for the first time in more than 40 years.

A spokeswoman said journey time is a "key consideration" in its delivery, which is still officially due to be completed by December 2014 but is widely expected to be delayed. The agency has declined to repeat an earlier commitment to ensuring journeys take no longer than 55 minutes, provoking alarm among senior politicians.

Michael Moore, the Liberal Democrat Borders MP and Secretary of State for Scotland, said he was "deeply concerned" by the rumoured cuts and has written to Scotland's Transport Secretary Keith Brown seeking reassurances on journey times.

Lorne Anton, chairman of CBR, said rail industry sources believed Transport Scotland was planning to reduce the length of passing loops along the route, which would increase journey times.

The campaign group has also raised concerns the design of the Borders railway will make it impossible for longer "tourist trains" popular with steam enthusiasts to stop at Tweedbank as the track is not long enough for them to stop at the platform.

In a letter to the Transport Minister, Mr Lorne warned against implementing cost savings in the initial scheme as these would be more expensive to rectify at a later date. "It has been suggested there would be later – post-opening – opportunities to put right initial deficiencies in the specification for the railway, but implementing enhancements in an operational railway is much more expensive than doing the job properly at the outset," he wrote.

The concerns were echoed by David Spaven, a rail consultant who has written a new book on the closure of the original Borders rail route in 1969, who added: "Transport Scotland have evidently asked Network Rail to change the infrastructure specification to shave capital costs.

"This will almost certainly mean that the long-promised '55 minutes or less' from Tweedbank to Edinburgh won't be delivered – making this one of the slowest train services in east-central Scotland."

A spokeswoman for Transport Scotland said: "These claims are inaccurate. Bringing benefits for local communities and businesses in Midlothian and the Borders remains the key consideration in our work with Network Rail towards delivery of this project.

"As we progress the detailed design our focus continues to be on journey time efficiency."

The Borders railway was originally due to be built by a private sector organisation but delivery was handed over to Network Rail, which owns and maintains the UK's track and signals, following the collapse of a Government tendering competition last year.

The company confirmed it was discussing the design of the project with the Scottish Government, but said there had not been any dialogue about reducing its benefits to save money.

A spokesman for the company said: "Network Rail is presently working with the Scottish Government to identify the best method to deliver the Borders Railway to their specifications. We will make further information available once the details of our delivery plan are finalised."