More than 100 inspectors across Wales could walk out for three days in December in protest at pay and conditions, potentially leaving supermarket shelves empty, their union has warned.

The Welsh inspectors, who ensure meat from animals and poultry slaughtered at plants across the country is fit for human consumption, are among 1,000 Meat Hygiene Service (MHS) workers in the UK voting on strike action.

David Bezzina, regional organiser for Unison in Wales, said: “We are confident we will deliver a significant ‘yes’ vote.” He added: “Three days of action could have an effect on the consumer, with a reduction in meat on the shelves.”

The MHS, which is part of the Food Standards Agency, said it has contingency plans in place to “minimise any disruption in the run-up to Christmas”.

But a spokeswoman for Unison in London predicted meat and poultry production could stop for the whole three days because, she said, it would be difficult for MHS managers to mitigate the effects of such a large walk-out through employing temporary staff.

A qualified MHS inspector must be on the premises in an abattoir or poultry plant while animals are slaughtered, reports Wales Online.

Simon Watson, Unison national officer for meat inspectors, said their employer had refused to pay an agreed rise unless they accepted sweeping cuts to overtime payments and changed to a “work anytime” system, which could see shifts or place of work changed at short notice.

Mr Watson said: “Meat inspectors work hard to make sure the meat on our plates is safe to eat but they are being pushed to the limit by excessive workloads, staff shortages and totally unacceptable levels of bulling and harassment. On top of all this, staff are now being denied an agreed pay rise unless they accept sweeping cuts to overtime payments and change to a work anytime system.”

It is understood strike action would be timed to cause maximum disruption, possibly leaving turkey, chicken, beef, pork and lamb in short supply at a time when demand is greatest.

There are around 130 Unison members in the MHS in Wales and around 80% are directly involved in meat inspections. Meat inspectors have a fixed site or work in one area, serving a cluster of abattoirs and poultry processing plants.

MHS chief executive Steve McGrath said he remained committed to securing a negotiated settlement.

He added: “Unison has initiated an industrial action ballot of its members without allowing its members the opportunity to review the latest proposals. As such, the MHS shared the latest proposals with all staff on October 27. These proposals are not based on a work anytime, work any place approach. We want to pay our staff fairly for the hours they work."