Jamie Oliver and Hugh Fearnley-Whittingstall have highlighted the differences between standard and free range chickens.

Supermarkets had braced themselves for a drop in chicken sales, which are worth £3.5 billion a year.

But they said they had not seen any negative impact on business.

A Tesco spokesman said: "This week, daily national sales of standard whole birds are running approximately 7 per cent above the November 2007 daily average."

Sales of its Willow Farm whole birds, which offer higher standards of animal welfare, are slightly up as a proportion of chicken sales.

Source: Telegraph.co.uk