Nestlé is cutting up to 300 jobs in the UK and switching production of the Blue Riband chocolate bar to Poland, a move that has angered unions. The Swiss confectioner said most of the jobs would be lost in Newcastle and York, during 2017-18, but that its sites in Halifax, West Yorkshire, and Girvan, Ayrshire, would also be affected.

The change will end 81 years of British production of the wafer snack, which was originally manufactured in Scotland but is now made in Nestlé’s Fawdon plant in Newcastle.

The company said: “These proposals are being made by Nestlé UK to ensure that these sites operate more efficiently and remain competitive in a rapidly changing external environment. Our factory in Kargowa, Poland, is a centre of excellence for this type of wafer-based product and is the logical place for us to propose Blue Riband production takes place [there] in the future.”

However, the GMB and Unite unions said the proposed cuts were savage and unacceptable, and urged the government to intervene.

“Nestlé are throwing people’s lives, and those of their families, into turmoil for the sake of increasing profit margins,” said the GMB general secretary, Tim Roache. “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.”

Nestlé said it expected most of thecuts to come from voluntary redundancies. The company has earmarked cuts of 143 jobs in York, 110 at Fawdon, 15 in Halifax, and seven in Girvan.

At Fawdon, which employs about 600 people, Nestlé produces a number of products as well as the Blue Riband bar, including Rowntree’s Fruit Pastilles, Fruit Gums, Jelly Tots, Rolos, and Matchmakers. The company also makes KitKat, Polo and Milky Bar in York.

Julia Long, Unite’s national officer, said unions would fight the plans to shed jobs. “We will be campaigning to save as many jobs as possible and pressing Nestlé to think again about these plans which will see the loss of hundreds jobs and the production of an iconic biscuit shipped to Poland,” he said.

“Rather than turning its back on its UK workforce, Nestlé should be investing in its UK operations and keeping production here at plants in the UK. Over the coming days we will be scrutinising the company’s business rationale for these job losses, and explore alternatives to its cut-and-run approach.”

Nestlé, which employs more than 8,000 people in the UK, said it would begin a 45-day consultation on the proposals with unions and workers’ representatives as soon as possible.

The company added: “Nestlé UK appreciates that this is an uncertain time for employees and will work hard to ensure all are supported through this difficult period.”