Transport Secretary Ruth Kelly is said to have grown increasingly interested in the future of the Woodhead tunnel, a five-mile link between Sheffield and Manchester that could prove the key to introducing a new high-speed or specialist freight line into the region.

As it stands the Woodhead tunnel, opened as a prestige electrified line in the 1950s but closed in 1981 and unused since, is about to house a 400kv electricity cable which the National Grid says is essential to keeping Manchester powered.

Cables are currently run through Victorian tunnels parallel to the newer tunnel but have come to the end of their life and will be replaced in a £50m project expected to start next year.

National Grid says it would be impossible to lay new cables in the tight, deteriorating Victorian tunnels while keeping the power to Manchester running – and it needs to use the newer, wider and safer tunnel.

But campaigners say the 1950s tunnel provides an ideal route for a new rail line between the two cities, and allowing National Grid to lay its cables next year will close the door.

In a Parliamentary answer last week Ms Kelly said she was "committed" to keeping "all options on the table" and was in active discussions with National Grid on the tunnel's future.

But she also said it would be possible to run trains and electricity cables through the tunnel together – something no side believes possible – which forced the Department for Transport (DfT) to issue an embarrassing clarification afterwards.

However, sources have told the Yorkshire Post that Ms Kelly, who last year failed to respond to a letter from the Yorkshire and Humber Assembly pleading for help in saving the tunnel, has taken it upon herself to personally find a solution.

The National Grid last night said it would be happy to work on a compromise.

Spokeswoman Stephanie VanRosse said: "Anything is possible if the political will is there but we're not getting the message from official channels that we need to stop work and have a rethink.

"The bottom line is that we need to keep the lights on in Manchester, now and in the future. Our assets have come to an end of their life and unless there are definite plans in place to reopen the tunnel as a rail line then we can't go any further than we have."

One option would be for the National Grid to run the lines overland via electricity pylons, which would be cheaper than strengthening the tunnel.

But as the land covered is in the Peak District and the company has a policy of not building in national parks, it would need a firm sign from the Government before National Grid could proceed down that route.

Pressure to keep the tunnel available for a future railway line is growing. Sheffield Hillsborough MP Angela Smith has secured the support of 60 MPs in her campaign to stop National Grid moving in.

She said: "Pressure is growing on the Government to force National Grid to look again at its plans for the Woodhead tunnel. I intend to step up the campaign myself to secure an adjournment debate in Westminster in order to take the matter further."

A spokesman for the DfT would not comment last night on Ms Kelly's involvement.