The UK's big four supermarkets have all said they are committed to sourcing foods locally as much as possible.
Local is best for fruit and other produce, says the report
Tesco, Asda, Sainsbury's and Morrisons were responding to a report which said it was most environmentally friendly to buy food that had been made locally.
The report in the journal Food Policy criticised the environmental damage of transporting food long-distances.
Each of the big supermarkets said they had policies to encourage and increase their supplies of local produce.
A Tesco spokesman said the company was "committed to trying to source locally whenever possible, the seasons allow and there is customer demand".
He added that Tesco sells some 7,000 locally produced products, and has two dedicated local buyers in Scotland and Wales.
"All our products are marked with their country of origin, and within the UK, often their region and local areas of origin."
The report's authors - Professor Jules Petty and his colleague Tim Lang from City University - say that people should try to buy food from within a 20km (12-mile) radius.
They calculated that if all foods were sourced from within this radius, environmental and congestion costs would fall from more than £2.3bn to under £230m, due to the reduction in transportation or "road miles".
'Help for producers'
Asda said it has a dedicated local sourcing unit that is separate to its main sourcing department.
"Across the UK we have 200 local suppliers, many of which are very small indeed, employing less than 20 people," said an Asda spokesman.
"We try and make it as easy as possible for small firms to supply to us - we do not require them to have a computer for example, only a fax through which we can send orders."
He added that Asda's policy was for all its stores to sell more products from their area - "for example, our Cornish stores sell more Cornish products, and our Welsh stores stock more Welsh products".
Waitrose is currently running two separate schemes to boost its provision and support of local products and producers.
Firstly, it has launched its Small Producers Awards 2005 competition to honour small businesses that make quality food and drink.
And secondly, it has started two trials to give customers the chance to purchase locally farmed fruit and vegetables.
These are running at its Kent branches and certain stores in Gloucestershire and Monmouthshire.
A spokeswoman for Sainsbury's said it was "aware that many of our customers want to buy local produce which reflect regional tastes and traditions and have a preference for food grown or reared locally.
"We are committed to giving our customers the diverse range of local foods they want and have a dedicated team who search for promising local producers as part of our local sourcing programme."
A spokeswoman for Morrisons said it was a "keen supporters of small, local and regional producers and have a number of local producers supplying our stores".