Royal Mail workers are to receive ballot papers for a vote on a national strike.
The Communications Workers Union (CWU) said it was issuing the papers to 120,000 workers that it represents.
The move follows months of local strikes across the country in a row over pay and job security.
About 20,000 staff have so far walked out since July and there is now an estimated backlog of 20 million letters and parcels waiting to be delivered – about a quarter of Royal Mail’s daily volume, the Times reported.
