The Consumers' Association has sold its 'not for profit' internet car import operation Carbusters.com for £1.3m.
The site has been sold to Bizzbuild.com.
The association was behind the 'Great British Rip Off' campaign designed to force vehicle manufacturers to cut new car prices and launched Carbusters.com to increase the pressure by undercutting manufacturer list prices.
The sale prompted a rebuke by the SMMT, which is calling for the money to given to charity. Chief executive Christopher Macgowan said: "I am appalled to learn that an organisation claiming to work for the benefit of its members should be making more than £1m on a venture that was described as 'not for profit'.
“We call on the Consumers' Association to end its Great British rip-off and give this bonus profit to the motor industry benevolent fund (BEN)."
The CA responded by saying it would keep the money, which will be paid over three years.
"The money is going to a registered charity - the Consumers' Association. We will use it to continue our campaign for fair car prices in the UK and to fund other campaigns in the consumers' interest," a spokeswoman said. "We didn't make any money from the Carbusters' operation."
The Consumers' Association says Carbusters.com sold 1,700 cars with an average saving of £3,000 per vehicle on manufacturers' list prices.
"We have sold the operation because to continue to grow it needs a company prepared to invest properly in it," the spokeswoman said.
The CA will continue to help manage the site, which will be co-branded with the Which? logo and Bizzbuild's.