POSTAL workers left thousands of people with delayed mail when they walked out on strike amid claims of bullying, harassment and intimidation.

The Middlesbrough delivery office workers were out on strike for around an hour this morning and only returned to their workstations following talks with union leaders.

As a result of the walk-out, the Communication Workers Union members are set to be balloted for industrial action over changes to working practices and conditions.

Staff claim they were left with no alternative but to take action as anger builds in the sorting office.

The maintain they are being forced to worker longer hours amid a culture of bullying.

Bob McGuire, North-East Regional Secretary of the CWU, said: "There was allegations of intimidation, bullying and harassment. The members were angry and upset and there was a lot of frustration about how they were being treated in the office and it took quite a while to settle them down and talk to them in a calm manner."

No other sorting offices in the region were involved in the wildcat action.

Royal Mail bosses branded the strike action unlawful and maintained they would ensure there was minimal disruption to postal services across the town.

A Royal Mail spokesman said: "Postal workers at Middlesbrough Delivery Office took unofficial, unlawful industrial action for a short time over operational changes which are part of a deal agreed with the CWU in 2007.

"However, at 9.50am staff returned to work and Royal Mail will do everything possible to minimise any impact on delivery services in the TS1 - TS5 postcode areas.

"Royal Mail takes a zero tolerance approach to bullying and harassment and always investigates when such allegations are received."