Richmond Council pocketed thousands selling lists of voters’ names and addresses to companies – but has no choice in the matter.

In the past five years the authority raked in £3,831 after selling the information to 26 organisations including estate agents, charities, solicitors and recruiters.

Anyone can view the electoral register in person but by selling an edited database of the information companies can send out thousands of unsolicited letters with just a few clicks of a computer mouse.

All councils have a legal duty to sell the edited register for a proscribed fee but people can chose to opt out of having their information passed on.

Councillor Tony Arbour said: “Local councils operate under the regulations set by Government and unless these laws are changed we are legally required to continue this practice.

“Councils which have attempted to introduce an automatic opt-out have faced legal action to change back.”

Privacy pressure group Big Brother Watch exposed the figures after a series of Freedom of Information requests and has condemned the practice and called for it to be scrapped.

The research discovered that Richmond was one of more than 300 councils that sold the register to 2,700 individuals and companies in the past five years, earning a total of more than £250,000.

Richmond was named as one of 19 councils which sold the edited list to between 25 and 49 buyers.

Councils in affluent areas were the biggest sellers of the register, with Westminster, Elmbridge, Kensingston and Chelsea all selling it to more than 50 buyers.

Councillor Stephen Knight said: “Councils have no choice but to make the edited electoral register available to everyone for a fee, including direct marketing companies by law.

“This means it is very important to tick the box on the registration form to opt out of being listed on this public version of the register. “The separate full version of the register is always available to political parties and those involved in the administration of elections but will not be available to marketing companies.

“It is time the government changed the law to remove this obligation from councils to sell this edited version of the electoral register altogether.”

Critics said the form did not make it clear what happens if you do not opt out and said the box to do so was too small.

The information also raised concerns that the sale of information could damage the electoral process as potential voters could be put off voting.