Royal Mail PLC on Thursday secured a court injunction over a potential industrial action announced by a union representing its employees.
When CWU did not call it off, Royal Mail lodged an injunction with the High Court, which was heard this morning.
The Royal Mail added that that because of the 2013 Agenda for Growth agreement, the CWU had no legal grounds to strike.
Mr Justice Supperstone, who granted the injunction, said: "I consider the strike call to be unlawful and the defendant is obliged to withdraw its strike call until the external mediation process has been exhausted". "The first step is selecting a mediator acceptable to Royal Mail and the CWU from a panel that was agreed by both parties under the Agenda for Growth".
Communication Workers' Union members were set to walk out at 11am on 19 October in a protest over pay, pensions and jobs. The move would affect postal deliveries and collections on the Friday and Saturday. The mediation process is expected to take until Christmas to complete.
Paul Wotton, secretary of the CWU's South West No.7 Branch covering the Bath area, said they were expecting "most members" to strike following the result of the national ballot. Almost three-quarters (73%) of the CWU's 111,000 Royal Mail employed members participated in the ballot.
Royal Mail said: "We are very committed to working closely with the CWU in order to reach agreement as a matter of priority".
"Royal Mail Group management have clearly moved away from the spirit and intent of our agreements and the empty promises of privatisation, and have suffered a huge vote of no confidence from their employees and CWU members as a effect".
The company has written to the CWU invoking a "legally binding external mediation process", and reiterating that any industrial action would be unlawful. The last mass industrial action among postal workers was in 2009. "We must work together to save it".