Staff at the CGNU print inplant in Basildon feel "insulted and angry" about the possibility of the site being sold to direct marketing and IT firm Opus Trust.
In a letter to PrintWeek, they expressed concern about their employment prospects under Opus.
They said the advantages of working under Norwich Union were "huge" due to benefits such as a pension, which they felt wouldnt be guaranteed under Opus.
They added that they were often sent home through lack of work while some CGNU departments sent their print elsewhere.
"Document Services Staff Basildon" have also sent the letter to directors of Opus Trust and CGNU, which refused to comment.
"Once we have received the letter, we will enter into discussion with our staff," said CGNU head of media relations Ian Frater.
The staff said they "were appalled that Norwich Union would even consider selling us to a company that had only been in existence for 18 months".
But Opus Trust said it had excellent financial backing from its parent company, Opus Portfolio, and would invest significantly in the Basildon inplant if it were to acquire it.
No decision has been announced about the sale.
Two weeks ago CGNU said it was in discussion with Opus Trust about the sale of the site (PrintWeek, 11 May).
Story by Jeremy Allen
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