The moderate Transport Salaried Staffs' Association has joined forces with the more militant unions, Aslef and the RMT. They are threatening to hold simultaneous strike ballots unless train operators and rail companies agree to a series of demands over the railway pension scheme's deficit of at least £590 million.

The first strike could be staged in early summer and would result in all 19,600 daily train services being cancelled. Travellers already face the threat of a strike by British Airways pilots this summer in a dispute that also concerns a pension deficit.

The last national rail strikes were in 1994, when signalmen alone managed to bring the network to a standstill.

The three unions are making detailed plans to ensure that their industrial action would involve all 22 train companies, affecting three million daily passengers. They fear that the rail companies are working behind the scenes to push the retirement age up to 65 and replace the final salary pension scheme with one based on career average earnings.

The three general secretaries, Bob Crow, of the RMT, Keith Norman, of Aslef, and Gerry Doherty, of the TSSA, will start their campaign on Monday at the TUC headquarters. They will also appear together at nine regional rallies.

Train operators have previously relied on deep rivalries between the unions to minimise the impact of strikes. But the unions have buried their differences and hope to use the pensions dispute as a conduit to reintroducing collective bargaining.

In an interview with The Times, Gerry Doherty, the general secretary of the TSSA, said: "There is going to be a huge row over the pension deficit.

"We are getting blanked by the industry and it has put us on a collision course. We are now preparing our tactics and would have simultaneous ballots and simultaneous action. If it comes to it, the whole network would be shut."

Mr Doherty said that the Association of Train Operating Companies had refused to talk with the unions, telling them that they must negotiate separately with each company. "This is a ploy to avoid engaging with us and make us use up our resources by holding separate talks," he said. The unions are demanding that the companies give a guarantee that employee pension contributions are capped at 10.56 per cent. Some branches of the rail pension scheme are so deeply in deficit that members face having to pay more than a fifth of their salaries in pension contributions.

An RMT spokesman said that the scheme had been undermined by the fragmentation of the industry since privatisation. Train companies held franchises for as little as seven years and had no incentive to take a long-term view.

He called on the Government to provide guarantees that would allow the deficits to be repaid over a longer period than the five years that is now being proposed.