The centre processes an estimated 1.2m letters and parcels every day

Exeter Mail Centre staff walked out on Tuesday in support of a union official involved in a dispute with managers.

Some people have returned to the sorting office but picket lines remain in place and national union officials are now handling the negotiations.

The Communication Workers Union says management will not discuss the issues which are at the centre of the dispute.

The strike was called after Royal Mail started disciplinary proceedings against a union official over his sick leave.

Workers say proper procedures were not followed, which Royal Mail denies.

Airport picket

About 300 workers walked out of the Exeter centre, which processes an estimated 1.2 million letters and parcels everyday.

The unofficial strike is affecting almost half a million homes in the EX and TQ postcode areas.

A picket line at Exeter Airport has delayed some mail being sent from Plymouth to other areas of the country.

Royal Mail managers have been helping to sort post since it began.

The company apologised for the disruption and said although talks had been constructive, they had concluded without agreement.

Phil Chadwick, the CWU branch secretary, said: "A complicating factor is that Royal Mail have now placed additional sanctions on the workforce on the duty rotation and conditions that they will work under on their return and that has severely complicated the return to work."

Royal Mail says the change brings workers in line with others across Britain.