Members of the CWU, Britain's fifth largest union, will stage a 48-hour walkout following a major row over pay and pensions.
Royal Mail head of network Andy Pickering said: "In the modern world, it is easy to forget that it can still take a long time to reach some destinations by land and sea". It said that this agreement contains contractual dispute resolution procedures.
He added whilst the CWU had hoped to avoid industrial action, the company "failed" to understand the gravity of the situation or make realistic offers in any of these areas. "If CWU does not withdraw its notice of strike action by 12 noon Monday October 9, Royal Mail will lodge an application with the High Court for an injunction to prevent industrial action", it said.
According to Royal Mail: "These legally-binding dispute resolution procedures were set up as a vehicle to resolve industrial disputes".
"We wish to use them to do just that".
"We don't want anyone to be disappointed if they are waiting for Christmas mail". Taking into account the 18,000 front-line employees who are not union members, 57% of Royal Mail employees backed the strike.
"Both sides are required to follow them once instigated". A clear mechanism for instituting these procedures is set out in writing in the Agenda for Growth.
Today Terry Pullinger, CWU's deputy general secretary (postal), blamed Royal Mail for the breakdown of talks which began early previous year and which have focussed on the corporation's closure of the final salary pension scheme to new entrants, as well as pay and plans to shut delivery offices.
"Royal Mail Group management have clearly moved away from the spirit and intent of our agreements and the empty promises of privatisation...", Pullinger said.
The union said the strike will involve around 110,000 workers across the UK.
The Communication Workers Union said it had told the Royal Mail Group that 111,000 postal workers will walk out.