Royal Mail is reportedly planning to begin a fresh round of cost-cutting that unions fear may trigger 40,000 job losses and a major switch from full-time to part-time work.
The postal group, whose markets were opened to competition this month, is trying to cut costs by £370m before April.
It has also begun wide-ranging talks with unions about cutting jobs by automating more functions and increasing the proportion of staff who work part-time.
At present 20% of Royal Mail workers are part-timers, but it is believed that this could double, reports The Times.
A spokesman for Royal Mail confirmed that it was looking at job cuts and more use of part-time staff, but would not comment on the size of the plans.
He said that automation would cut the need for labour and that competition would reduce Royal Mail’s workload.
“It is too soon to speculate on the size of Royal Mail, but it is no secret that we intend to be more efficient and flexible than our competitors,” he said.
Billy Hayes, the Communication Workers Union general secretary, accused Royal Mail of using competition as an excuse.
“Competition should not be an opportunity for the business to drive down pay and conditions and cut our jobs,” he said.