It announced the decision to staff at the plant this afternoon (11 December), and has begun consulting with the workforce and unions.
The future of Watford had been the subject of speculation for some time, and this was compounded earlier this year when Polestar opted to create a 64pp superplant at its Petty site in Leeds.
The Watford plant runs a new MAN Roland Lithoman IV 64pp web and an older short-grain 64pp. Both could potentially be relocated to Petty.
Watford employs 300 staff, and prints a number of weekly titles including TV Times and Whats on TV?.
In a statement, group operations director Mike Bartlett said: Polestar Watford and Petty serve similar markets and it makes sense to combine them now to create one cost-effective and efficient print factory. We continue to believe the future for Polestar is in a smaller number of much larger sites where we can achieve better scale and efficiency.
GPMU deputy general secretary Tony Burke described the announcement as "another blow to the printing industry". "I'm obviously very concerned for our members and their families, particularly at this time of year."
The union had been informed of Polestar's intentions and it will be meeting with the company to discuss the matter. Burke said he hoped to persuade the company to reverse the decision. "Polestar have said they are willing to listen to alternative proposals," he said.
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