Officials said there had been "precious few" responses to the unions' demands for a formula to end what they described as a "pensions crisis."

And Unions representing tens of thousands of workers at dozens of train companies and maintenance firms have warned that ballots for industrial action will be held if progress to end the dispute was not made by 4pm today.

The Rail Maritime and Transport union, Aslef, the Transport Salaried Staffs Association and engineering unions in the CSEU are campaigning to ensure that the Railway Pensions Scheme remains open to all employees and that worker contributions are capped.

The unions have warned that they want an agreement reached before "unacceptably high" employee contribution increases come into effect in July.

The dispute involves every train operator, Network Rail and dozens of infrastructure companies.

Gerry Doherty, general secretary of the TSSA, said: "Our members have packed into meetings around the country to tell us that they are not prepared to allow their pension scheme to disintegrate before their eyes or suffer the massive contribution hikes that will be triggered on July 1 if no agreement is reached.

"Doing nothing means accepting the eventual collapse of the scheme and the prospect of poverty in retirement. That is simply not an option and if it means industrial action, then so be it."

Leaders of the unions will meet over the next few weeks to decide their next move.

If a strike goes ahead, it will be the first industry-wide stoppage since the General Strike in 1926 and will cripple the rail network, causing travel chaos across the country.

A spokesman for Network Rail said: "Our scheme is sound and over the last three years we have worked with our employees and the unions to increase the scheme's funding levels and this has proved to be effective.

"Contributions for employees and employer will increase by a small percentage in the coming year to sustain the improvement in the funding position."