More than 115,000 Royal Mail workers will begin voting today over whether to go on strike over pay.
Ballot papers will be dispatched to the Communication Workers Union (CWU) members, with the result on 19 July.
Should workers vote in favour of industrial action, the CWU said it could amount to the biggest ever strike taken by its members this summer.
The CWC is the latest of several unions to ballot for strikes in recent weeks as the cost of living soars.
Prices are rising at their fastest rate for 40 years, with UK inflation at 9.1%, the highest level since March 1982.
Higher costs for fuel, energy and good are biting into household budgets and workers and unions are pushing for pay rises to cope with them.
But the government has warned against employers handing out big increases in salaries over fears of a 1970s style “inflationary spiral” where firms hike wages and then pass the cost on to customers through higher prices.
Britain’s railways were disrupted when thousands of RMT Union members walked out last week and hundreds of British Airways workers at Heathrow Airport have also voted to go on strike over their wages.
Separately, 114 Post Offices are to be closed on 11 July when workers strike over pay.
CWU deputy general secretary Terry Pullinger said in a video posted on Twitter the union wanted an “inflation-based, no-strings pay award” for its Royal Mail members.
“The company has imposed a 2% pay award, miles away from where inflation is, totally inadequate,” he said.
The CWU said the pay award was “despite previous agreements that no immediate executive action would be taken over pay”.
“Throughout this entire dispute, Royal Mail management have conducted themselves insultingly and disrespectfully to key workers,” Mr Pullinger said.
“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.”
CWU general-secretary Dave Ward said CWU general secretary Dave Ward said he expected members to “deliver a historic vote for action”.
But Royal Mail said it believed there were “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,” a spokesman said.
The company said further talks were scheduled with CWU this week and it hoped an agreement could be reached.