Union officials are holding talks with senior managers at British Sugar to try to keep the firm's York factory open.
British Sugar announced earlier this month that it planned to close the processing factory, which employs more than 100 full-time staff.
It said there was not enough sugar beet being grown in Yorkshire for the factory to run at full capacity.
But staff and their unions do not accept that and are challenging senior managers at a meeting on Thursday.
John Kirk, regional organiser of the GMB union, said before the meeting he had asked the National Farmers' Union to assess the situation, as he believed beet volumes in Yorkshire were sufficient.
British Sugar also plans to close its processing factory in Allscott, Shropshire and centralise work at four sites: Cantley and Wissington in Norfolk, Bury St Edmunds in Suffolk and Newark, Nottinghamshire.
The York site, which opened in 1926, is likely to close at the end of next year.