Local politicians have reacted with dismay over plans to cut nearly 300 jobs at the Dow chemical works in Barry.
According to union officials, the corporation is blaming 'cheap compeition' from China as it looks to save around $6 billion worldwide.
The move arounds a third of Dow's Barry workforce - with a consultation involving 291 workers now underway.
Labour MS Jane Hutt said she had spoken with company chiefs following Monday's announcement, which she described as "extremely disappointing".
The outgoing Senedd member for the Vale of Glamorgan said: "Dow has been a key employer for Barry for decades and this news will be a shock to the loyal, highly skilled workforce serving Dow."
She added: "There must be meaningful consultation and clarity about how long the site will be functioning and what can be retained and safeguarded."
Ms Hutt said she would be visiting the works alongside Vale MP Kanishka Narayan to meet with Unite union representatives.
On Monday, the union called on Dow to overturn its decision, calling on the corporation to work with them to prevent compulsory redundancies.
It's believed no job losses will be made before the middle of next year.
Former Welsh Conservative leader Andrew RT Davies, MS for South Wales Central, said: "Yet again, British workers are suffering the consequences of globalisation, losing out due to cheap Chinese competition."
"These are good quality jobs and it will be a hammer blow to the economy in the Vale. I am raising this urgently with company bosses and urge them to reconsider this move."
Shadow Economy Secretary, Sam Kurtz, gave a similar reaction warning cheaper overseas imports were leaving Welsh workers bearing "the negative consequences of globalisation".
He said: "Unless we address the barriers that are undermining business competitiveness, whether excessive taxation, overregulation or arbitrary net zero targets, we will continue to see Welsh jobs exported abroad, to the lasting detriment of our communities."
“The world is changing faster than ever. If Wales and the United Kingdom are to keep pace, we must urgently strengthen the competitiveness of our domestic industries.”
A Dow spokesperson said siloxanes production was one of several manufacturing facilities and operations as its Barry site, which employs around 850 people.
They added: "This potential shutdown would help strengthen the Company's competitive position in the specialty silicones market in Europe and the UK."
"The production of specialty silicones in Barry will continue, supporting key markets such as automotive, electronics, energy, construction, and personal care."
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