The Communication Workers Union today revealed that 75% of members who voted in the strike ballot were in favour of the move. According to Royal Mail the CWU balloted 127,000 people and 66,064 voted for action.
Union members have rejected Royal Mail's offer of a pay rise of 2.5%, with a possible bonus of £800 and a 50% share in any above-budget cost savings achieved locally.
The CWU is seeking further negotiations with Royal Mail rather than immediately calling a strike.
However, Royal Mail put out a statement after the vote saying it would continue its drive to modernise the business.
Allan Leighton, chairman of Royal Mail, said: "If we don't modernise we'll fail...so our position remains -- we can't afford to pay any more right now and we certainly can't afford to put all our future in danger by putting off the need to change and modernise."