About 80 engineers at the company’s factories in Kettering and Corby will take part in a series of one day strikes during June, July and August.

The strike action has been organised by union Unite, which is calling for the controversial ‘fire and rehire’ practise to be banned.

Weetabix has issued the engineers with new contracts and work patterns, which Unite says will result in major cuts in shift allowances. There will also be a move to require more day working than shift working, further contributing to the cut in pay.

Some of the affected engineers will lose up to £5,000 a year. There are also major concerns about health and safety of the workers at both plants due to the low number of engineers who will now be on duty at certain times.

Sean Kettle, Unite regional officer, said: “Weetabix and its US parent company Post Holdings are incredibly profitable and are not facing any financial difficulties. Our members are well aware that these fire and rehire attacks are simply an opportunistic response to the uncertainty caused by the pandemic.

“They are incensed at the company’s unacceptable behaviour, which is especially galling given their pivotal role in keeping Weetabix’s plants operating during the worst of the pandemic. The strikes will impact Weetabix supplies this summer and it is expected there will be shortages in the shops.

“Industrial action can still be prevented if Weetabix withdraws its fire and rehire threats and engages in constructive negotiations with Unite’s representatives.”

Other companies which have been accused of using fire and rehire to pay staff less include British Gas and coffee firm Jacobs Douwe Egberts.

The Trades Union Congress (TUC) recently found that one in 10 workers had been threatened with fire and rehire during the pandemic. Unions fear this number will grow dramatically as furlough ends unless the law is changed.