Hundreds of jobs at the Birds Eye frozen food factory in Hull will be lost following an announcement today that it will close later this year.

Birds Eye, which is moving its UK fish production range to Germany, said there would be 490 redundancies from a workforce of around 600.

The plant, which produces millions of fish fingers and fish cakes each year, is in the west Hull constituency of the education secretary, Alan Johnson. Last year, Mr Johnson said he would "do his best" to try to keep it open as Birds Eye reviewed its sites.

Today, the GMB union accused the firm of a "cynical" move, citing assurances about jobs given when Unilever sold the European part of Birds Eye to venture capitalists Permira in August last year.

"Unfortunately, workers in Alan Johnson's constituency have now been hit by the curse of the venture capitalists," John Wilson, a GMB official, said.

The Birds Eye chief executive, Martin Glenn, said: "When Unilever sold the business, it was agreed that employees' terms and conditions would be honoured for up to three years. This includes redundancy terms.

"We are honouring our part of the bargain and are now consulting on the best deal for those workers affected by today's announcement."

The GMB reiterated its complaint that venture capitalists had favourable tax arrangements on interest payments even though they "destroyed" the livelihoods of workers.

Birds Eye blamed excess capacity in its supply chain, particularly fish, for the closure decision. Its fish foods range will now be produced in Bremerhaven, Germany, and Lowestoft, Suffolk, where it has a food freezing factory.

Some staff at the Hull factory, which was opened in 1967, would be given the opportunity to transfer from Hull to Lowestoft, Birds Eye said.

"We have inherited a business that has unsustainable over-capacity," Mr Glenn, said. "The frozen food market is increasingly cost-driven. To be competitive, you require large-scale, highly efficient production facilities.

"The future success of our fish category can be best served through the consolidation of our production facilities into our larger and more efficient sites in Bremerhaven and Lowestoft."

The frozen foods sector has been hit by consumer moves towards fresh and chilled produce, which are seen as healthier.

Ian Kelly, the chief executive of Hull and Humber Chamber of Commerce, said the factory closure was "very sad news". "These are skilled and talented workers who have made a good profit for their business over the years," he added.