Traditional BOGOF deals have been criticised for wasting food as people throw away freebies they have not got around to eating before they have gone off. But with Tesco's promotion, you buy one and get a voucher for another you can pick up another time. The vouchers, which are only for perishable items, last months.

Tesco executive director Lucy Neville-Rolfe said: "Customers really like our Buy One Get One Free deals but feedback shows smaller households sometimes can't use the free product before its use-by date.

"Now we're giving customers the flexibility by claiming their free product the following week instead. As well as giving our customers a flexible new offer, we're helping them to cut food waste."

British households throw away £420-worth of food each year and the government wants to reduce that.
Sainsbury's has a similar voucher deal on some products. But according to Friends of the Earth food expert Helen Rimmer, it is "staggeringly hypocritical" for supermarkets to claim the high ground on environmental issues, and it will take more than replacing BOGOFs with BOGOFLs to make them look green.

Others have said it is just a scam to get us back into the Tesco the following week clutching our vouchers high above our heads, thinking we have got one over on the supermarket, when really we are the dupes.

Tesco has other enviro-measures. It has dropped prices for low-energy lightbulbs and is looking at ways to encourage customers to buy low-impact washing powder. It will also offer points on its Clubcards for buying "carbon conscious purchasing". Whatever that means.

It also sends out green auditors to people's homes to offer free advice on insulation, double glazing and fitting solar panels. But you have to be a bit of an idiot not to realise that insulating your loft and adding double-glazing will cut down on energy use, so will these people even remember what the auditor said the moment after they close the door behind them?