Britons may struggle to get hold of a free-range turkey or goose for the Christmas table this year after an industry head said about half of them have either died or been culled due to the country’s largest-ever outbreak of avian flu.

Richard Griffiths, chief executive of the British Poultry Council, told lawmakers that British farmers usually produce 1.2 to 1.3 million free-range birds for the festive period.

“We have seen around 600,000 of those free-range birds being directly affected,” he said.

Giving evidence to parliament’s Environment, Food and Rural Affairs Committee, Griffiths said total turkey production for Christmas in the UK was usually about 8.5 to 9 million birds. Of these, just over one million have died or been culled.

He did not know what the impact would be on prices.

“That is really a question for retailers at this point. We do not know how the gaps within retail are going to be filled,” he said.

The major supermarket groups have so far been relatively relaxed in their public statements about turkey availability at Christmas.

Market leader Tesco TSCO.L said in October it expected to be able to satisfy demand, while earlier this month Sainsbury’sSBRY.L said it had ordered more turkeys for Christmas this year than last year, giving it a buffer in case the crisis did hinder supply.

Also, Marks & SpencerMKS.L, which typically sells one in four fresh turkeys consumed in the UK at Christmas, said it had strong plans to protect supply.

However, poultry farmer Paul Kelly told the committee, “there will be a big, big shortage of free range British turkeys on the shelves this year,” noting “the biggest effect has been on the supermarkets.”

Griffiths said that since the beginning of October there had been nearly 140 cases of bird flu in the UK, with 1.6 million birds culled.

He said 36% of poultry farms in the UK were now subject to avian flu controls, which means birds must be kept indoors.

“So it’s huge and the .. costs for industry and food production are potentially enormous.”