Network Rail says the public are against a strike

Pay and pension disputes mean about 7,000 Rail Maritime and Transport Union members are expected to back a walkout.

The RMT says it may join strike action by train workers with London Underground strikes, where its members are involved in a separate pay row.

Rail industry bosses have said every 24-hour strike would cost over �12m.

A co-ordinated strike could spark the worst bout of industrial action on the railways for over a decade.

RMT general secretary Bob Crow is expected to announce the ballot result later on Thursday.

Stalemate

Sources within Network Rail have warned every 24-hour strike would cause losses of between �12m and �15m.

"Every single day the RMT is on strike, the pay available to settle the dispute goes down. The 3.5% being offered by Network Rail is worth �21m, so that would be wiped out within two days of a strike," a source said.

The RMT is also lobbying Network Rail to end its refusal to offer a final salary pension scheme to new entrants.

Mr Crow said: "Network Rail are under pressure to save money and they are trying to do it at our members' expense.

"They have imposed a cheaper and inferior pension scheme on new starters without a word of negotiation, purely to save money," he added.