Environmentally aware consumers are more likely to lie, cheat and be unkind than regular shoppers, a study suggests.

Researchers say that people have a limited stock of goodwill and that being virtuous in one part of life leads to meanness in another. The phenomenon called 'compensatory ethics' came to light in a series of experiments carried out by psychologists at the University of Toronto, reported dailymail.co.uk.

'People act less altruistically and are more likely to cheat and steal after purchasing green products as opposed to conventional products,' said Nina Mazar, who led the study.

Mazar's team paid 90 volunteers $5 to take part in an experiment designed to find out whether green consumption affects morality.

The students were split into two groups and told to buy goods in either a normal online store or an internet store selling environmentally friendly products. The green consumers were found more likely to cheat at a simple computer game than those who used the conventional store.

And when they were invited to take a certain amount of money from an envelope as their reward, the green shoppers tended to take more cash than they were entitled too.

The authors report in the journal, Psychological Science: 'The halo associated with green consumerism has to be taken with reservations. While mere exposure to green products can have a positive effect by inducing prosocial and ethical acts, purchasing green products may license indulgence in self-interested and unethical behaviours.'

Other tests found volunteers behaved more honestly when shown green products, but not when they had to buy them.