Trade union Unite said its members had been told that a pay offer agreed with the site’s previous owners had been revoked by Italian conglomerate Newlat.

Unite general secretary Sharon Graham said: “If Princes thinks its threats will weaken workers’ resolve it has another thing coming. This is appalling behaviour from a shameful company.

“First it pulled the rug from under our members by reneging on a pay deal and now it is threatening their jobs with these union-busting tactics.

“Unite won’t stand for such tactics and will be backing our members every step of the way in their dispute.”

Angelo Mastrolia, the board chair, said continuing industrial action could have a “hugely detrimental impact” on union and non-union members.

He said all options to maintain the sustainability and stability of the company must be considered.

The chairman said the firm faced increasing costs, including the rise in employer National Insurance contributions.

Mr Mastrolia added: “Should Unite confirm the strike schedule for February, Princes will be forced to withdraw the 3% offer.

“Furthermore, we will be compelled to transfer part of our branded production to other facilities, including those abroad, and if the strike action continues, this will likely become a necessary choice for the future, which could mean a need to reduce jobs at our UK sites.

“This is a very real risk, which benefits neither the workers nor the company”.