Colman's Mustard - its factory in Norwich is under threat of closure.
UK-based soft drinks company Britvic is planning to shut down one of its manufacturing sites in Norwich.
"We need to make Norwich as cost-effective and I will be asking the government to do all they can to keep Britvic and Unilever".
The companies behind Robinsons squash and Colman's mustard are set to close their manufacturing facilities in Norwich, putting more than 350 jobs at risk.
"The Unilever has today announced a review of the whole site to be concluded by the end of November".
Britvic announced it had tabled proposals to transfer production of Robinsons and Fruit Shoot to sites in east London, Leeds and Rugby, this morning.
'Britvic and Unilever's operations have been uniquely intertwined at the site for many years, relying on a shared infrastructure. Colman's has been an important part of Norwich and the surrounding area for more than 200 years and, whatever the outcome of the review, we will work hard to retain this link.
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It said one of the choices considered in the audit would "incorporate the potential conclusion of our Norwich processing plant".
Britvic said it would embark on a consultation process with the 242 affected staff before the site's proposed closure at the end of 2019.
Production at the Chelmsford factory ceased in 2014. The company said that while grocery performance was subdued, it grew strongly in the convenience and on-trade channels.
However, Britvic clarified that its three-year £240m investment into its United Kingdom manufacturing operations remains on track and would not be affected by the Norwich move.
"Join won't just look for confirmations, however applying weight with the goal that the creation and the genuinely necessary employments that are key for the Norwich economy remain".
National officer Rhys McCarthy said: "The sad news that Britvic is closing its operations in Norwich also has an impact on Unilever workers who the share the same site".
Colman's was founded in Norwich in 1814 and its mustard has been made in the city ever since.