Leaders of the Rail Maritime and Transport (RMT) union decided to call a strike ballot in protest at a pay offer and the imposition of a new pension scheme.
The union said the pay deal was worth 3%, describing it as the worst in the railway industry and complaining that new workers were being given an inferior pension scheme. The two sides are also in dispute over travel facilities for workers.
"The company has closed a decent pension scheme and imposed a glorified savings plan on our members, has refused to negotiate at all on travel facilities and has tabled the worst pay offer in the industry this year," the RMT's general secretary, Bob Crow, said.
"This is a company which on one hand boasts of spending £14m a day, yet on the other says it cannot afford to maintain a decent pension scheme or end the divisive inequality in travel facilities.
"The company talks about cutting costs, but its directors will top up their six-figure salaries with more fat bonuses for squeezing the pay of the people who actually go out and get the work done.
"Network Rail's short-sighted stance means a two-tier workforce with staff doing the same job getting different conditions and vastly different pensions. Even those left in the old pension scheme will have to pay out ever-increasing contributions to maintain their benefits as fewer and fewer workers are left paying in."
Network Rail said the threat of industrial action was "astonishing" and insisted that talks had not broken down.
"We find the strike threat nothing short of astonishing as we are in the middle of constructive pay negotiations. There has not been a breakdown of talks. A variety of good deals are on the table for the unions to consider," said Network Rail's chief executive, John Armitt.
Network Rail said it had offered three different options, including a pay rise of 3.5% and the offer of a 35-hour week.
