Royal Mail workers have voted overwhelmingly in favour of striking in a dispute over job security and employment terms and conditions, raising the threat of industrial action in the run-up to Christmas.
Members of the Communication Workers Union (CWU) backed action by 97% in a huge turnout of almost 76%.
The CWU said Royal Mail was not sticking to an agreement reached last year covering a wide range of issues, including plans to reduce the working week, as well as job security.
Industrial relations at the company have worsened this year, with widespread unofficial strikes breaking out virtually every week.
Terry Pullinger, the CWU’s deputy general secretary, said the union and its members were facing the “fight of our lives”.
The CWU said the result represented the largest vote in favour of national industrial action since the passing of the Trade Union Act 2016.
The union said the prospect of the first national postal strike in a decade now “looms large”.
Pullinger said: “Just over one year ago the Royal Mail Group Board and the CWU agreed a blueprint agreement for the future, a progressive agreement that included a historic pension solution, a mutual interest driven relationship and a joint vision for a successful postal service with social aims.
“Today the new RMG leadership are breaking that agreement.
“Our members take honour seriously and have voted to fight for that agreement against those who now seek to break up the great British postal service in the interest of fast-track profit and greed.
“Integrity and pride still matters and we will not stand aside and see what we have spent our working lives building destroyed.”
Dave Ward, the CWU’s general secretary, said: “This result sends a clear message to Royal Mail Group – our members will not stand by as you rip up their terms and conditions and destroy the service they give to the public and businesses of the UK.
“We would urge Royal Mail Group to now enter serious negotiations with this union. We also call on the public to get behind this dispute and your postal workers.
“We are very proud of our members today. They have stood by their union in record numbers and given hope to workers across the nation.”
The Labour leader, Jeremy Corbyn, said Royal Mail was an example of a “privatisation failure” following news of the strike action.
“Thousands of posties have voted yes in record numbers for strike action in defence of their jobs,” he tweeted. “Royal Mail is a Tory-Lib Dem privatisation failure.
“Its selloff led to shareholders creaming profits off the top while running down the service.”