The union, which represents postal workers, served the notice today (21 June). Ballot papers will be dispatched on 28 June and the result will be known on 19 July.

The decision came after delegates at the union’s April annual conference voted to declare the beginning of a national dispute in early May if a “straight, no strings pay increase” failed to materialise.

CWU said further tensions among the workforce grew last week after Royal Mail Group said it intended to impose a 2% pay rise by executive action, “despite previous agreements that no immediate executive action would be taken over pay”.

“In an economic climate where inflation is set to soar to 11.1% by the year’s end, this would mean a real-terms wage cut of approximately 9% for Royal Mail employees,” CWU stated.

Pullinger commented: “Throughout this entire dispute, Royal Mail management have conducted themselves insultingly and disrespectfully to key workers.

“Their conduct, and particularly the imposition of such an aggressive pay offer, has eroded trust among loyal employees.

“Nobody wants to be in this situation, but our members are heroes.

“We will defend ourselves if provoked – and we are convinced we will receive our biggest ever Yes vote for action.”

In response, Royal Mail said that following the conclusion of negotiations with CWU, including completing the mutually agreed Dispute Resolution Processes, on 15 June the company said it would award CWU grade colleagues a non-conditional 2% pay increase backdated to 1 April 2022.

It said CWU grade colleagues will receive a first payment as a lump sum that covers a 2% increase from 1 April 2022 to 31 August 2022 in their pay on 1 July 2022 if paid weekly or 30 July if paid monthly. From 1 September onwards, colleagues will continue to receive the 2% increase, consolidated into base pay, in their regular weekly or monthly pay.

Royal Mail said it also informed CWU that a further 3.5% is available, subject to the two parties agreeing on a series of changes and a new ‘above and beyond’ bonus. To do that, Royal Mail said there needs to be agreement with CWU on the critical changes that are required to pay for further pay increases.

A Royal Mail spokesperson said: “We believe there are no grounds for industrial action. We offered a deal worth up to 5.5% for CWU grade colleagues, the biggest increase we have offered for many years, which was rejected by the CWU.

“We have further talks on change with CWU this week. We hope this will ultimately lead to an agreement on the changes required to ensure Royal Mail can grow and remain competitive in a fast-moving industry, securing jobs for the future and retaining our place as the industry leader on pay and terms and conditions.

“We value the work we do with CWU and remain committed to agreeing a deal for tomorrow, not just today.”