Customers who pre-ordered organic turkeys were offered a £10 voucher

The supermarket has written to 1,300 customers who had pre-ordered organic birds offering them a £10 voucher and the chance to switch to free-range.

Waitrose buys organic turkeys from two farms on the Norfolk-Suffolk border where culls were carried out.

A spokeswoman said the chain would still stock non-organic free-range and Select Farm own-label turkeys.

"Waitrose sources all its turkeys from known farms and we are not prepared to compromise those principles by buying turkeys on the open market," she said.

"Organic turkeys make up a small proportion of our total turkey requirements."

She added: "The two farms we source from were impacted by avian flu."

Many of the customers contacted by Waitrose asked for their £10 gift vouchers to be donated to the affected farmers, she added.