Norwich South MP Clive Lewis has joined trade unions in vowing to fight plans to transfer production of Robinsons squash and Fruit Shoot drinks away from Norwich.

The proposals, announced last month, would see manufacturer Britvic move production to plants in London, Leeds, and Rugby and cease manufacturing in Norwich in Autumn 2019, a move which would see the loss of 242 local jobs.

The Bracondale factory is co-owned and operated by Britvic and Unilever, manufacturer of the iconic Colman’s Mustard brand which has been produced at the site since the 1860s.

After Britvic announced its proposal to leave Norwich, Unilever revealed it was also reviewing the futures of its 113 members of staff at the plant, taking the total number of jobs at risk to over 350.

According to the GMB trade union’s regional organiser Ivan Mercer, Mr Lewis promised that he is “committed to offer every assistance to overturn this proposal by Britvic”. The MP has visited the factory to speak to some of the employees who would be affected and met with bosses from the company.

Mr Lewis told the Eastern Daily Press: “Jobs in manufacturing are hard to come by in Norwich and this is going to be a blow, but it is not a done deal.

“Britvic in particular said no decision would be made prior to consultation, and I am going to hold them to that, as I am sure the local authorities and trade unions will.”

GMB, which has an estimated 150 members among the Britvic workforce and around 60 from Unilever, said it was “very concerned” and described the threat of job losses as “not just a blow for Norwich but Norfolk manufacturing in general”.

Union Unite also have members working for both firms. National officer Rhys McCarthy called the Britvic announcement “very painful” and said Unite “will be giving the maximum support to our members at what is a very difficult time in the days and weeks ahead.

“Unite will not only be seeking assurances, but applying pressure with the support of the local community, that the production and the much-needed jobs that are vital for the Norwich economy remain.”

Britvic CEO Simon Litherland claimed: “The changes we are proposing present significant productivity and efficiency savings in our manufacturing operations, deliver environmental benefits and, coupled with our ongoing investment programme in our GB manufacturing operations, ensure that we have the flexibility and capability we need to respond to changing consumer trends faster and more efficiently.”

Talks over the site’s future are ongoing, although GMB has expressed concerns over the validity of Britvic’s consultation as the firm is already investing heavily in its Rugby branch, one of the potential destinations for production currently based in Norwich.

The announcements sparked an EDP campaign to keep production in Norwich.

It has so far seen over 11,000 signatures on a petition and Norwich City fans don their old kits from when Colman’s were the club’s shirt sponsor.