Up to a third of workers at Greencore’s UK plants at certain times of the year are paid at or close to the minimum wage.

Most are agency staff, who are not employed directly by the company.

Greencore chief executive Patrick Coveney has defended the food company's pay rates and its use of agency staff following a major row over its employment practices in England.

The Irish food group sparked an angry debate about immigration and workers' rights in Britain after admitting it went to Hungary to recruit low-cost staff for its flagship sandwich factory in Northampton.

Mr Coveney – a brother of Minister for Agriculture, Food and the Marine – admitted in an interview with The Irish Times that low-paid agency staff accounted for up to 30 per cent of the workforce.

Greencore also said less than 10 per cent of the company’s directly employed workforce was employed on the minimum wage and that no-one was kept on this rate for longer than three months.

Mr Coveney said the sandwich maker was operating in a highly competitive sector and that its pay rates were in line with industry norms.

“We’re operating in an industry where retail prices for products are falling and we have to be very competitive on all the components that go into our costs,” he said.

“We pay at least as much as our competitors and in many cases more, and we have better levels of retention, better levels of engagement and more training programmes and benefits for workers than our rivals.”

The Dublin-headquartered company, which now ranks as the largest manufacturer of pre-packed sandwiches in the world, ran into a storm of protest when it claimed it could not get local people to fill the positions in Northampton.

The comment was seized upon by some to suggest the British government’s immigration laws were leading to an influx of low-skilled migrant workers while the relatively generous welfare system was disincentivising people to work.

The controversy also brought Greencore’s employment practices into the firing line, in particular its use of low-paid agency staff, who are typically employed on minimum wage rates of £6.50 an hour, which workers’ rights groups claim is too little to live on.

Mr Coveney also defended his own £2 million (€2.5 million) pay packet, saying his remuneration was set by the Greencore board in consultation with shareholders, who vote on it.