A postal strike could drag on for weeks or months with managers drafted in from as far afield as Bristol to keep the service going.

About 130 workers at the sorting office in Bognor Regis held a one-day strike yesterday, the third since industrial action started on May 20.

They are striking over pay, hours and working conditions.

Union officials claim Royal Mail promised it would improve the building then went back on the agreement because of spiralling costs.

Another three 24-hour strikes are planned for June 18, June 25 and July 2.

Richard Tabbner, of the Communications Workers' Union, said: "The office hasn't had any investment for 18 years.

"The improvements would let our members work five days a week instead of six and have a £28 pay rise per month.

"We are the only sorting office in the country still working a six day week for £272, everyone else works five for more money."

He said Royal Mail had offered to give staff the same hours and pay as at its 1,300 other sorting offices but workers had still chosen to strike without pay because they wanted to see the service improvements the renovation would have generated.

He said: "Our members were offered £500 in back pay if they accepted no change in deliveries, but we stood by the agreement.

"They lose a day's pay for every day they are on strike and 130 people don't take that decision lightly.

"The service is not being maintained during the strikes. During the last stoppage there was a 20,000 item backlog."

Royal Mail denies the union's version of events. A spokeswoman said money had already been spent on improvements and the firm offered to hire 13 extra employees to allow workers to move to a five day week.

She said: "We are surprised and disappointed local members decided not to support the agreement reached by the managers."

John Stamp, chairman of the Bognor Regis Chamber of Commerce, said the effects of the strike were being felt in the town, adding: "I didn't get a single item of mail today so it is not as sweet as they think it is."

June 9, 2005