Cutting 500 jobs from Hull's Birds Eye factory will be a "devastating blow" to the area, a minister has said.
Birds Eye employs 1,250 people at sites across the UK
Education Secretary Alan Johnson said he shared the dismay and anger felt by some over the closure of the plant.
The company blamed what it called unsustainable capacity in its supply chain for shutting the factory, which is in Mr Johnson's constituency.
Birds Eye said its foods would now be produced at sites in Bremerhaven, Germany and Lowestoft, Suffolk.
The company said 490 redundancies were involved, but the GMB union said it understood 600 jobs would be lost and described the announcement as "grim".
Mr Johnson, who is MP for Hull West and Hessle, said he had been working with the unions for several years to try and secure the future of the plant.
He said: "I share the dismay and anger of the workforce over the decision to close the plant.
"This is a devastating blow for a loyal and productive workforce."
He added that he would be helping to press for the best redundancy packages possible for the workforce.
Employees were given the news during a morning meeting on Thursday with chief executive Martin Glenn at the factory.
The Birds Eye company employs 1,250 people at sites across the UK.
The processing plant in Hull was established in 1967 on a 17-acre site.
It has seven main production lines turning out foods such as fish fingers, fish cakes and peas.