Network Rail tonight made legal moves in a bid to avert a crippling strike by signal workers after Easter.
The company served papers on the Rail, Maritime and Transport union calling into question the validity of a ballot, even though peace talks were being held in a bid to resolve a row over jobs.
The union's 12,000 NR maintenance members voted by 77% in favour of strikes, while its 6,000 signallers backed industrial action by 54%.
The union, and the Transport Salaried Staffs Association, announced four days of strikes from next Tuesday, threatening major disruption to rail services.
The unions are protesting at plans to axe 1,500 maintenance jobs and change signallers' working practices.
NR said in a statement tonight: "Network Rail has a responsibility to all our passengers and freight users, and to the country as a whole, to do everything we can to avert a strike. Talks continue and our aim is a negotiated settlement, but we must explore all avenues at our disposal and that includes legal ones.
"We can confirm that papers have been served on the RMT this afternoon. This calls into question the validity of its ballot amongst our signallers, highlighting scores of discrepancies and inaccuracies.
"We will appear before a High Court judge tomorrow afternoon."
NR sources said talks this week at the conciliation service Acas on the maintenance dispute had been "constructive" and the company hoped they would continue.
Bob Crow, RMT general secretary said: "We spent two days in constructive talks, making some serious progress and Network Rail has chosen to sabotage that process by using anti-trade union laws to drag us to court.
"We ran a perfectly above board ballot of our members and we have every intention of defending our position."Reuse content