The Grimsby factory is set to close early next year

The GMB staged the demonstration outside the Tate Modern in London on Tuesday as part of a campaign to save jobs at the town's Birds Eye site.

Unilever, which owns Birds Eye, was staging a reception at the museum to mark the opening of a sound exhibition.

The Ladysmith Road site is to close early next year.

'Kick in teeth'

Sandra Allen, a GMB shop steward who has worked at the Grimsby factory for 15 years, said: "Our workforce has been an exemplary model of partnership with Unilever management.

"We have won awards for learning and skills development, revolutionised health and safety procedures and supported the company through two huge restructuring initiatives.

"Our reward will be over 600 kicks in the teeth."

Plants in Hull and Lowestoft will both remain fully operational following the review into operations at Birds Eye.

But the Grimsby site was deemed to be too small to be competitive in the ready meals market.

Unilever said it would have preferred to sell the factory but efforts to do this had failed.

The company also looked at a proposal to invest in the site, but decided this would not be economically competitive in the long term.