Companies begin to put carbon footprint figures on their products, and Walkers Crisps is the first to go ahead with the idea.

Customers can now have full details of the impact that the food item they are taking off a supermarket shelf can put on the body.

Walkers Crisps has started labelling its onion bags and cheese with a carbon footprint in the month of April. The labelling gives details of the amount of greenhouse gases produced for the production of the product.

A private company, the Carbon Trust, which is created by the government to cut the UK's carbon footprint, did all the calculations.

After spending several months, it calculated that for producing a 33.5g bag of Walkers crisps, 75g of greenhouse gases are emitted.

Nine other firms including Cadbury and Coca-Cola are committed to follow Walkers after the methodology implemented by the Carbon Trust gets approval next year.

Euan Murray of the Carbon Trust said, "Ultimately the aspiration is that everything you can buy will have a carbon measure with it - 75g is the first number out there and actually there's not much context for it. But when we can start making comparisons across different products, then we can make choices as consumers".

The carbon footprint label comes with a two-year promise to cut the carbon footprint.

A spokeswoman for Walkers says that their own research shows that about 80 per cent of consumers appreciated the labels while 20 per cent dismissed it saying purely a gesture.