Union Unite, which is leading the industrial action, says that from 8 November, strikes will take place every Monday, Tuesday, Wednesday and Thursday.

Around 80 Weetabix engineers have been on strike every Tuesday and Wednesday since September over cuts to their pay, terms and conditions that the union says will cost some workers more than £5,000 a year. There were also a number of one-day strikes in June, July and August.

Unite warned that increasing the strike action, which has already closed production lines and put orders several days behind schedule, will cause further disruption to Weetabix’s operations.

Sharon Graham, Unite general secretary, said: “Weetabix is making bumper profits so there is no justification for these ‘fire and rehire’ attacks on our members’ wages and conditions. They are just not swallowing what in reality is a serving of corporate greed.

“Unite will not accept attacks on our members jobs, pay and conditions and Weetabix should expect this dispute to continue escalating until fire and rehire is dropped.”

As well as industrial action, protests at supermarkets across the UK are also being held to raise awareness of Weetabix’s actions. Unite said the protests are necessary because shoppers will want to know that “Weetabix has tainted its good name by attacking our members’ living standards while raking in massive profits”.

Unite said Weetabix has performed very strongly since the beginning of the pandemic. In 2020, its turnover grew by 5% to £325m and profits leapt by almost 20% to £82m.

The latest accounts of Weetabix’s parent company, Post Holdings Inc, the US cereal giant, show that in 2020 it had a turnover of $5.7bn (£4.2bn) and an operating profit of $701m (£518m). Its cash reserves are $1.2bn (£890m).

Unite regional officer Sean Kettle said: “Our members’ determination to fend off these unjustified pay grabs is rock solid, and Weetabix’s reputation will continue to be damaged until it withdraws them.

“Polling shows 70% of people disagree with fire and rehire, a practice which leaves an especially bad taste in the mouth when it’s conducted by a company that bills itself as the ‘nation’s favourite’.”