Heinz has announced plans to close its factory in Grimsby with the loss of up to 405 jobs.
The company has not been making money from frozen pizzas
The food manufacturer says that its pizza manufacturing site is no longer viable.
Despite a £10m investment in the plant since they acquired it from United Biscuits in 1999, the business has lost money.
Heinz blames a lack of demand for its pizzas in an increasingly saturated market.
It said there had been a continuing decline in production volumes leading to an under-utilisation of the factory.
Director of Heinz Frozen Foods Division Mark Holdaway said the company "deeply regretted" having to consider closing the Grimsby site.
He said: "This proposal is difficult but necessary, and was only made after careful consideration of possible alternatives.
Heinz is the UK's fourth-placed pizza manufacturer on the market.
The Grimsby site, one of 37 Heinz plants in Europe, produces pizzas under the San Marco and Ross labels.
But while other areas of the business have been performing well, its frozen pizzas have lost money.
Mr Holdaway added: "The proposal is based on the economics of production and capacity under-utilisation at Grimsby."
Heinz will enter into a consultation process with employees and their unions. Local MPs will also be kept informed.