UP to 20 people are likely to be made redundant at the Glaxo pharmaceutical factory in Barnard Castle.
Discussions are now underway to decide who will lose their jobs at the GlaxoSmith- Kline plant.
About 1,100 men and women are presently employed there - several hundred less than the total who worked there in the past, when the jobs were regarded as the most secure in Teesdale.
The company announced proposals to change ways of working at the factory "as part of a continuing drive to improve operational efficiency".
A company spokesman said the changes will include a reduction of up to 20 staff, adding: "This will be dependent on the outcomes of consultation and the selection processes.
The aim of the selection process is to retain key skills and knowledge, minimising the number of redundancies."
One employee, who did not wish to be named, said: "This is really bad news. The workforce has been severely reduced in previous years and we hoped to have seen the end of redundancies.
"Twenty may not seem a high number but it is causing a lot of anxiety as nobody knows who will have to leave. The fear is that the axe will fall around Christmas time and that some senior staff will be going."
The company announced in February that more than 300 jobs would be lost at its factory at Ulverston, Cumbria, as part of a worldwide exercise to reduce costs by £700m by 2010.
It was stated at the time that no job losses were expected in Barnard Castle, but that they could not be ruled out.
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