And women are no more ethical than men when it comes to shopping.
The survey found that young and old people were less likely to buy fairtrade and organic goods at supermarkets.
The findings go against the commonly held view that people become more ethical as they get older.
Researchers found that younger shoppers talked a lot about buying ethical goods, but failed to practice what they preached.
The survey also found that younger people recommended ethical products more than older consumers, but were less likely to buy them.
And despite the perception that women are more ethical than men, the survey found no difference between the shopping habits of the two genders.
Study leader Professor Kevin Morrell, of Warwick Business School, said: “There is the perception that in general people become more ethical as they get older or that today’s young are more in tune with ethical buying and the environment.
“But we were surprised to find that it was the middle-aged who were the ethical shoppers.
“We found a ‘curvilinear’ relationship between age and purchasing fairtrade and organic products: both older and younger respondents were less likely to purchase ethical goods than middle-aged respondents.
“Age was also associated with the extent to which people would recommend fairtrade goods, with the oldest respondents also being least likely to recommend fairtrade products to others. This also suggested that younger shoppers were not entirely ‘practising what they preached.
“Overall, we did not find that gender had any effects on recommendation or purchasing of fairtrade or organic food.”
In the study, published in the Journal of Marketing Management, Professor Morrell, Chanaka Jayawardhena, of Hull University Business School, and Chris Stride, of the University of Sheffield, questioned 688 shoppers at three UK supermarkets.
Just over half of those surveyed were women (53 per cent), just under half aged under 30 and around 20 per cent aged 50 or older.
Prof Morrell added: “The findings may reflect that both younger and older consumers have less disposable income, especially as fairtrade and organic goods are often more expensive.
“Certainly, it might explain why younger shoppers recommend ethical foods, but don’t then buy them as they simply can’t afford it.
“Older shoppers might just be more engrained in their shopping habits and not as aware of the move to fairtrade and organic foods. Or it might be that younger and older shoppers are purchasing from a smaller pool of products than those middle-aged consumers doing a family shop.
“It may also reflect that there is greater awareness of some of these pro-social issues among younger consumers and that older shoppers are more settled in their shopping habits.”
He said the findings have implications for marketers and organisations aiming to promote fairtrade to tackle the exploitation of workers and those looking to protect the environment and animal welfare.
Prof Morrell added: “Our work shows that values play an important part in how many consumers shop, with many aware that their buying habits can have a direct impact on people’s working conditions or the environment.
“Marketers need to take that into consideration and make sure it is part of their marketing mix.
“We know a lot of decision-making in supermarkets is almost sub-conscious and so ethical shopping could be enhanced by useful visual cues and subtle features in the layout of the store that could align with these values.”