Unilever faces a fortnight of industrial action after unions stepped up their protests over changes to the company’s pension scheme.

The three trade unions representing workers – Unite, USDAW and GMB – announced on Saturday (7 January) that up to 12 days of strikes involving thousands of workers will take place from 17 January onwards. They said the stoppages will hit production of the global giant’s leading brands, including Marmite, Pot Noodle and Hellman’s mayonnaise.

The unrest stems from changes to the final salary pension scheme, which unions say will cut the retirement income of thousands of staff by up to 40%. Last month, workers across the country downed tools for a day-long strike.

Jennie Formby, national officer of Unite, said: “It would seem that Unilever believed the workers would give up after one day’s strike but they are badly mistaken. The workforce is angry that the company has refused to meet us or to attend talks at the conciliation service Acas.”

Meanwhile Allan Black, national officer of the GMB, warned of further strikes unless the row is resolved.

Unilever said it is “deeply concerned” about the announcement and called the union’s actions “disproportionate”.

A statement added: “This was a tough but necessary choice which reflects the realities of rising life expectancy and increased market volatility. We believe the provision of final salary pensions is a broken model which is no longer appropriate for Unilever. It is our responsibility to protect the long-term sustainability and competitiveness of our business, and to do so is in the best interests of our people.

“It is currently not clear how the dispute with the trade unions will be resolved – but we are continuing to urge our employees who have participated in industrial action to give further objective consideration to the very competitive new arrangements.”

A spokesperson added that the company has prepared for this industrial action and there will be no impact to the supply of its brands.