The Shepton Mallet cider mill is set to close, with its production being moved to Ireland, according to its owner, Dublin-based C&C Group, whose brands include Gaymers and Blackthorn.
Wells MP James Heappey told the BBC: "This is a devastating blow for Shepton Mallet. The job losses [thought to be 127] are significant and that will be my first concern."
A Unite press release which followed the announcement this Tuesday stated that the announcement of the mill closure had been communicated in "A Dickensian" fashion.
According to the Unite release, workers at the Shepton Mallet cider mill learnt about the planned closure of the site from media reports, with the cider mill representatives only being informed in the afternoon.
The Unite report goes on to say that the owners of C&C want to move production of cider to its Magners plant in Clonmel in Tipperary but fruit will continue to be pulped at Shepton Mallet, then shipped to Ireland.
Unite regional co-ordinating officer Steve Preddy said: "It is disgraceful and Dickensian that this dedicated and loyal workforce should hear of the closure through the media.
"There has been more than 240 years of cider production at Shepton Mallet at a workplace that is synonymous with historic cider production in the South West - and now this is coming to an end.
"This is a grievous blow to the workforce, their families, the town and the Somerset economy.
"We will be seeking an urgent meeting with the management for the reasons behind the closure and what can be done to safeguard jobs at the site, given that pulping will continue in Somerset. We will be giving our members Unite's maximum support at this traumatic time."
C&C Group has also announced its other site in Borrisoleigh, Tipperary, will close with the loss of 54 jobs, with production and packaging all moving to Clonmel.
A spokesman for the firm told the BBC: "The trading environment in the UK and Ireland has been intensely competitive over recent years.
"This has led to significant downward pricing pressure and the loss of material contracts for private label water."
The firm added the closures had been a "difficult decision", adding the Clonmel site was the only viable option to maintain long-term competitiveness.
"Shepton Mallet is the global centre of the cider industry and we now face the real prospect of cider no longer being produced in the town and that would be an incredible shame," added Heappey.
A closure date has not been confirmed and company's website appears to be offline.