Engineering workers at the Heinz frozen potato factory at Westwick, near North Walsham, are holding the first of a series of one-day strikes today in a dispute over shift changes.

Engineering workers at the Heinz frozen potato factory at Westwick, near North Walsham, are holding the first of a series of one-day strikes today in a dispute over shift changes.

Workers at the plant, which produces Aunt Bessie's roast potatoes, plan to walk out every Thursday for the next four weeks.

Mark Robinson, regional officer for the union Amicus, said 21 members were taking part in industrial action out of the total workforce of 130.

He said: “Amicus is taking industrial action 10am today as a result of company imposition of a 12-hour shift rota from August.

“This will have the effect of increasing weekly hours from 39-42 hours a week and will reduce the shift premium for new starters by 14.5pc.

“Despite our assurances that we were prepared to cover the factory on a 24/7 basis with an eight-hour shift rota, the company has declined this offer.”

A spokesman for Heinz said the planned changes in shift patterns would simply align the engineering teams to the same shifts successfully adopted by all production workers.

He said: “A continuous shift pattern, with 12-hour shifts and an average of 42 hours per week, was first introduced in production areas at the site in 2002.

“The new shift pattern was successfully adopted by 2004 by manufacturing process staff to cope with increased production volume and improve efficiency.

“Discussions began with the engineering union and engineering teams last year with a view to transfer from a mixture of eight and 12-hour shifts to a continuous shift pattern to support their colleagues in production.

“The plans were rejected by the engineering team along with alternative patterns proposed to the membership by the union and considered by the company.

“The arbitration and conciliation service, Acas, was also involved earlier this year but no agreement could be reached despite assurances to match current shift premiums to ensure consistency and fairness.

“Production workers are not supporting any form of industrial action and will not be affected. At the present time impact on production is likely to be minimal.”

The future of the Westwick site was only resolved in May when Heinz announced it was keeping the operation.

Heinz had put the plant and its sister factory at Fakenham up for sale after deciding they were no longer core businesses.

It sold the Fakenham site, which produces vegetarian food under the Linda McCartney brand to US speciality foods business the Hain Celestial Group, but decided the Westwick site still had a future under Heinz ownership.