Industrial action could force the closure of British Sugar factories this autumn, workers’ representatives have warned.

Beet processing could be halted at factory sites within five weeks unless a pay dispute is resolved, said the union Unite. If workers down tools, it would be the first time in 30 years that British Sugar has been hit by strike action.

Unite is due to start balloting 250 members on industrial action next week – just days before processing plants open on 14 September at Bury St Edmunds, Cantley, Newark and Wissington. The ballot result will be known by the end of the month.

“We are probably a month or five weeks away from taking action,” Unite regional officer Tony Ellingford told Farmers Weekly. “We have the capability of shutting down any or all of the four factory sites without a doubt.”

Union members have rejected a 3.5% pay offer by British Sugar. Instead, they want a pay deal tied to retail price inflation. Mr Ellingford said: “British Sugar is a profit-making company but expects employees to take a drop in their standard of living.”

The union is asking its members to vote on two proposals. The first proposal is a ban on overtime. The second proposal would see workers take strike action on days chosen to cause maximum disruption to beet processing.

Mr Ellingford said: “There is always the possibility that they will vote for one or the other, but we are asking them to vote ‘yes’ to both. We will pick the days when industrial action will have most impact.”

In a statement, British Sugar said it was awaiting the outcome of the ballot. It added: “British Sugar has undertaken all necessary steps to mitigate any disruption to our four processing factories and the delivery of our products to our customers.”

Farm leaders are keeping a watching brief on the situation. NFU sugar adviser Lee Abbey said: “We are not getting involved in this – it is a matter between British Sugar and its employees.”