Around 100 unionised workers at the plant implemented an overtime ban at the start of July.

The workers’ union, Unite, has now warned DTF that more severe strike action will be taken unless the company improves its pay offer.

DTF’s original offer, which sparked the dispute, was worth around 3.1%, and was made directly to workers in what Unite called a “shameful” bypassing of established bargaining processes.

The manufacturer turns over around £100m from its UK arm, and is a major supplier of PET films to the packaging, labelling, digital printing and medical industries.

Products include Melinex film used for applications including durable labels, roll-up displays and banners; and the Mylar range of packaging films used for printing, converting and metallising. 

Sharon Graham, Unite’s general secretary, said: “The imposition of a wage offer on the DuPont workforce in Dumfries is totally unacceptable.

“Just over 3% does next to nothing to help our members in this cost-of-living crisis.

“DuPont also shamefully bypassed the agreed bargaining processes and Unite representatives to impose this offer. 

“If our members take the decision to escalate their industrial action, then they will have their union’s full support in the fight for better jobs, pay and conditions.” 

DTF’s UK operation recorded profits after tax totalled £2.9m for the year ending 31 December 2021, down on £10.7m the year before. In its accounts, DTF cited raw material, energy and operating costs for the decrease.

Printweek has approached DTF for comment.