Critics have branded Hilary Benn's call for an end to bogofs "idiotic", as research for The Grocer shows supermarkets have already significantly cut back.

At this week's launch of the Defra food strategy, the environment secretary said bogofs were a major cause of food waste and should be phased out for half-price and money-off deals.

But Assosia research shows supermarkets have largely eliminated bogofs in many categories. Bogofs now comprise just 11% of featured space offers in the big four, down from 17% last August, while Asda has dropped them entirely.

Retailers have also cut 3-for-2 style promotions from 40% to 26% of all offers as money-off and half-price deals rocket. More than a third of promotions are now money-off deals, while 13% are half price.

"Led by what customers want, we've moved toward price-led promotions such as 25%-off and half-price offers," said a Sainsbury's spokeswoman. "Bogofs are now only about 10% of our promotions and the vast majority are on store-cupboard items such as baked beans, cereals and coffee not perishables."

Supermarkets added that bogofs were now often mix-and-match deals in long shelf life categories.

"Benn's aim is to reduce food waste but the proposal is idiotic from start to finish," said David Rawcliffe, a research fellow at free-market think tank the Adam Smith Institute. "Even if it does reduce waste, a ban wouldn't help anyone. The market allocates food pretty efficiently. "Supermarkets offer bogofs because it makes them richer and people buy them because it makes them happier. Banning them will eliminate mutually beneficial trades and make both groups worse off."

Supermarkets hit a Wrap target last year to reduce food waste by 100,000 tonnes and are on track for a further cut of 150,000 tonnes by 2010. Wrap does not consider bogofs a major contributor to waste and is focusing instead on domestic food storage and best-before labelling.

See Analysis, p12