Nestle is on the brink of cutting nearly 300 jobs as part of plans to shift production of its Blue Riband chocolate biscuit to Poland, unions have said.
Unite union and GMB union said that Nestle was using the Brexit vote as a reason to cut jobs and "trample on workers' rights".
Jobs may be lost in York (143 jobs); Fawdon in the North East (110 jobs); Halifax (15 jobs) and Girvan, Scotland (7 jobs). If the cuts go ahead, they will take place over the next two years.
Nestle said it is hoping the job losses will be achieved through voluntary redundancies.
"These proposals are being made by Nestle UK to ensure that these sites operate more efficiently and remain competitive in a rapidly changing external environment," Nestle said.
"Nestle UK appreciates that this is an uncertain time for employees and will work hard to ensure all are supported through this difficult period."
The business is now undertaking a 45-day consultation with staff and trade unions on the proposals.
The news comes shortly after drinks giant Diageo said it is axing more than 100 jobs in Scotland due to its concerns over Brexit. PepsiCo has also said 380 jobs are at risk as it prepares to shut its Walkers Peterlee factory.
Tim Roache, GMB general secretary, said: "To shift the production of an iconic British brand like Blue Riband is completely unacceptable.
"These factories should be exporting chocolate - not people's jobs. The government needs to step in before it's too late, and reassure millions of workers across the country this is not just the tip of the Brexit iceberg."