The Hull factory made ready meals for sale in supermarkets
Northern Foods is planning to close its Hull factory putting the jobs of 349 employees under threat.
The firm said the Brighton Street site was not viable after it lost a contract to make ready meals for its main customer - supermarket chain Morrisons.
It said it had not been able to agree terms with Bradford-based Morrisons.
The company, which makes Goodfella's pizzas and Fox's Biscuits, said it would now begin a 90-day consultation process with employees on its proposal.
Chief executive Stefan Barden said: "The loss of this contract makes the site commercially unviable.
"We are today announcing a proposal to cease production and close the site."
Mr Barden said: "We do not take this decision lightly and fully recognise and regret the uncertainty this will bring to our loyal employees.
"Our immediate task is to support our staff through the consultation period at this difficult time."
Although the company has other production sites throughout Yorkshire and the north of England, the ready meals market has been in decline for the past two years.
Last year it also mothballed Fenland Foods in Grantham which makes Italian ready meals, after it failed to agree a deal with the factory's customer, Marks & Spencer.
News of the Hull site's demise came as the Leeds-based group announced a 5% drop in pre-tax profits for the year to 28 March to £47.5m.