The trade union Unite has asked the Department for the Economy to investigate the alleged use of agency workers at Pilgrim's Europe's Enniskillen factory during ongoing strike action. The union says it has formally complained to the department's employment agency inspectorate, requesting an immediate investigation into the number of agency workers at the site and whether they are carrying out duties normally performed by employees involved in the industrial action.

Workers at the Enniskillen factory are now in their sixth week of strike action over pay and what Unite describes as a two-tier system of paid breaks. The factory produces food products including Fridge Raiders, Richmond and Denny sausages.

Unite claims the industrial action has significantly impacted production at the site. The union alleges that the number of workers being transported to the factory by bus from Armagh has surged in recent weeks. It has also raised concerns after employment agency Staffline Group plc allegedly advertised positions at the Pilgrim's factory for immediate starts.

Under the Conduct of Employment Agencies and Employment Businesses Regulations (Northern Ireland) 2005, Unite says it is a criminal offence for employment agencies to supply labour to employers specifically to cover work normally undertaken by employees taking part in lawful industrial action.

Unite said it wrote to Staffline on July 28 to formally advise the agency of its responsibilities under the regulations. The union has now written to the Department for the Economy's employment agency inspectorate calling for an investigation.

Unite general secretary Sharon Graham said the company was desperately trying to continue production rather than provide workers with what she described as a fair pay increase. "It's illegal to bring agency workers in to cover striking workers and this matter must immediately be investigated and action taken," Graham said.

Unite regional officer Greg O'Kane said: "Over the last few weeks, we know the number of workers being bussed into Pilgrims daily from Armagh has surged. In recent days, the agency posted advertisements for immediate start positions at the factory. The Department for the Economy needs to act urgently to ensure the right of workers to undertake lawful industrial action is protected."

On August 28, Unite wrote to the organisation asking it to investigate concerns relating to production at the Pilgrim's factory during the ongoing industrial dispute.

A spokesperson for Pilgrim's Europe said there is "no basis to Unite's claim which we have only learned about through the Union's press release. We are fully satisfied that we are operating in accordance with the law as we seek to mitigate the impact of strike action amongst a minority of employees at our Enniskillen site."

Staffline Group plc has been contacted for comment.