Unfairly maligned as smelly, difficult to cook and riddled with potentially throat-lacerating bones, at one time it seemed that Britons had fallen irrevocably out of love with fresh fish as a culinary staple.

After the Second World War, fishmongers steadily disappeared from the high street and a generation of home cooks turned their backs on the fruits of the sea.

However, growing concerns over healthy eating and its enthusiastic promotion by celebrity chefs have resulted in an extraordinary comeback. Fresh fish has now overtaken chicken at one of the UK's leading supermarket chains to become the most popular source of protein in the shopping basket.

Waitrose reported a 20 per cent year-on-year rise in fish sales, compared to a 6 per cent increase in the sales of poultry.

The figures are even more revealing because the poultry industry had been celebrating the public's determination to keep on buying chicken in the wake of the bird flu crisis earlier this year.

According to Waitrose, which accounts for 10 per cent of the UK's £1.8bn annual fish sales - three times its share of the grocery market - the figures show that consumers are taking on board the Government's healthy eating recommendations, as well as responding to reassurances over sustainability.

The Food Standards Agency recommends eating at least two portions of fish a week, one of which should be oily, as part of a low fat diet and as a source of omega-3 fats which help reduce heart disease.

Waitrose's specialist fish buyer Jeremy Langley said: "Fish is a fantastic addition to a healthy diet and has become a mainstream addition to our customers' shopping baskets. But coupled with this surge in demand is a pressing need for retailers to ensure that their fish is sourced in the most sustainable way possible."

All of Waitrose's cod and haddock - the two most popular white fish - is caught on lines rather than trawlers, he said. The chain now wants to phase out beam trawling, a practice that involves dragging a heavy net across the sea bed and damages the marine environment.

The Marine Conservation Society's spokesman, Richard Harrington, said the increase in fish sales must not come at the cost of endangered stocks.

The UK fishing fleet saw landings fall by 55 per cent from the 1960s and by the millennium, species such as cod were on the brink of collapse while skate, turbot and monkfish were also in trouble. Meanwhile, swordfish and types of tuna stocks fell by as much as 90 per cent, it was estimated.

Conscientious consumers have been advised to try coley, grey gurnard, hoki and cape hake as an alternative to threatened species.

Mr Harrington said: "The MCS welcomes the increasing popularity of fish as a healthy and sustainable source of food as long as fish sold comes from healthy stocks and are caught using methods that minimise harm to sea life."

Fish was at its most popular after the Second World War, when Britain had 9,000 fishmongers. Their numbers have dramatically declined as developments in poultry rearing saw chicken become the most popular, and cheapest, protein source. Today supermarkets account for half of all fish sales, and demand has increased with the advent of chilled meals and the growth in popularity of farmed salmon. However, despite the best attempts of celebrity chefs such as Delia Smith, whose How To Cook series included a chapter on "Fish Without Fear", seven out of 10 people still do not eat the recommended two portions of fish a week.