Network Rail is issuing a legal challenge to one of the unions threatening to strike over the bank holiday.
It has asked the TSSA rail union to withdraw notice of industrial action, saying there are “numerous defects” in its ballot.
The move came just before talks were due to resume on averting a strike by thousands of workers over pay.
The TSSA union, which represents white-collar staff, said its members voted strongly in favour of industrial action.
Network Rail (NR) said in a statement: “We have asked the TSSA to withdraw notice of their industrial action as we believe there are numerous defects in their ballot information.”
Members of the Rail, Maritime and Transport (RMT) union are also planning to strike, warning that train services will be at a standstill next Tuesday if the 24-hour walkout goes ahead from 5pm on Monday.
Talks were held for six hours at the conciliation service Acas yesterday and are due to resume later today.
Manuel Cortes, leader of the TSSA, said: “We are frankly puzzled as to why NR are taking this legal route whilst talks continue today at Acas to solve this dispute and avert next week’s strike action.
“They seem more determined to impress (Transport Secretary) Patrick McLoughlin and the Tories than making a serious attempt to resolve this pay row and ensure that the trains run on time over the bank holiday.
“We want to settle this around the negotiating table, not in the High Court.”