The prospect of a national post strike came closer today when workers voted heavily in favour of industrial action in a row over pay.
About 130,000 members of the Communication Workers Union are now set to stage a series of walkouts unless fresh talks lead to a breakthrough in the deadlocked dispute.
The union announced at its annual conference in Bournemouth that ballots of three separate groups of Royal Mail workers showed overwhelming support for strikes.
Union leaders will meet next week to draw up plans for the first national strikes since 1996.
The union is in dispute with the Royal Mail over pay after leaders rejected a 2.5% pay offer in response for a demand that postal workers’ pay should rise to the national average over the next five years.
The Royal Mail said the demand amounted to a 27% pay rise which the organisation "simply can’t afford".
CWU deputy general secretary Dave Ward said: "Royal Mail workers have rejected the company’s business plan, the company’s leadership and an unacceptable pay offer.
"This is the clearest message we have had from the workforce so the Royal Mail has to listen, and return to serious negotiations."
The union held three ballots, covering 127,000 Royal Mail workers and two separate groups of employees involved in pay and jobs disputes.
About 5,000 union members working in Post Offices were balloted in protest at closures, pay and moving post offices inside WH Smith stores.
Royal Mail cash handlers, who deliver money to branches, also voted on a strike.
A Royal Mail spokesman said: "The result of the ballot will not change the absolute need for Royal Mail to modernise, which is in the interests of everyone in the company.
"Mail volumes have already fallen and more people are using electronic communications. Royal Mail has to become a modern, efficient business to ensure we compete effectively in a mail market where rivals are already 40% more efficient and will this year be handling one letter in five posted."
Royal Mail said it had made a "realistic and fair" offer comprising a 2.5% increase in basic pensionable pay, plus an #800 dividend from its ColleagueShares scheme and a 50% share in any savings above budget in an employee’s local unit.
The Royal Mail said the union’s claim would cost Royal Mail #1 billion.