Consumers are being threatened with paying the price for unhealthy dietary choices with a proposed 'fat tax'.

The move has been suggested by the Labour party in a bid to cut down on the number of obese citizens in the UK. In addition to customers' supermarket receipts telling them how many loyalty points they have, and how much they have saved on price promotions, receipts will now also tell them how much they have been taxed for the unhealthy items in their basket.

With 20 per cent of the UK adult population currently clinically obese, this number is predicted to rise to 50 per cent by the year 2040. Medical experts warn fat may well become the UK's biggest killer. One shocking statistic is that an average 10-year-old will eat his or her own body weight in chips in just nine months.

This week the left-leaning policy forum Demos will urge the government to consider the introduction of a new tax on unhealthy foods in an attempt to curb UK shoppers' poor dietary decisions.

Foods intended to carry extra levy include those with a high fat and sugar content, and processed and fast foods. Demos proposes the money raised should be channelled back into promoting healthier foods like fruit and vegetables.

However, a study into the UK's eating habits found many low-income families are 'trapped' into eating mass-produced processed meals because of time and money constraints. Demos believes the 'fat tax' would be a useful means of tackling 'food poverty', as healthier foods are currently more expensive.

A Demos spokesman said: 'Just as it has been used for discouraging smoking and drinking, so we could use tax to encourage people to eat more healthily by providing a disincentive for unhealthy foods. Also there is no incentive to eat fruit and vegetables, particularly for those on low incomes.' Another suggestion comes from Oxford University's health promotion group, where Dr Mike Rayner proposes an extension of VAT and EU subsidies rather than an overall 'fat tax'.

He said: 'At the moment, for example, you pay tax on a KitKat but your Jaffa Cakes come tax-free. There is no tax on cakes and biscuits. I would like to see us eating fewer cakes and biscuits, less meat and more fruit and vegetables, but the system goes against it.' Speaking for the British Dietic Association, Dr Wendy Doyle is concerned the move to tax unhealthy foods will disuade people from cooking adventurous recipes, and favours a simpler educational approach.

She said: 'We don't want to turn ourselves into a police state where the government tells us what to eat. The best way of changing habits is through educating people to cook properly and eat well.'