Charity shops should be exposed to the same commercial realities as other traders, according to the Federation of Small Businesses.
"Regulatory bodies and local authorities take a soft approach to charity shops," said Stephen Alambritis, head of parliamentary affairs at the federation.
"We have no problem with fair competition, but we are concerned at the extent to which they are selling brand new goods, with second-hand goods pushed to the back of the shop."
His comments follow complaints by Macclesfield councillor Joan Barnes that charity shops in Alderley Edge, Cheshire, were lowering the tone and benefiting from unfair trading advantages.
"This is adding to the deterioration of the shopping centre," said Barnes.
"It is not fair trading. They are not trading in a way standard commercial business is trading. They are not competitive and are in many cases claiming relief on business rates."
Charity shops are entitled to a mandatory 80 per cent business rates rebate, funded by central government, with the remaining 20 per cent at the discretion of the local authority.
Alderley Edge has three charity shops - Barnardo's, Cancer Research UK and Marie Curie Cancer Relief. Jo Stetzel, press officer at the Association of Charity Shops, said: "More should be done to encourage local charity shops on high streets.
"Although the profits go to charity, they are a business enterprise meeting a local need. Charity shops keep high streets busy and are a valuable resource."
UK charity shops generate £100m profit a year
Total sales exceed £440m a year. There are more than 6,500 such shops in the UK
100,000 volunteers work in shops across the country
More than 90 per cent of sales are from items donated by the public.
This is why shops are entitled to the business rates rebate.