Councils have been accused of cashing in on people's names and addresses - leading to a mountain of junk mail.
More than 300 local authorities sold versions of the electoral register to more than 2,700 private companies and individuals, including pizza shops, lobbyists and estate agents.
Campaigners said this led to unwanted letters, with most people unaware their details had ever been passed on.
They called for a change in the law to make it easier for people to opt out.
Nick Pickles, director of Big Brother Watch, which revealed the figures, said: "Registering to vote is a basic part of our democracy and should not be a back door for our names and addresses to be sold to anyone and everyone.
"Many people don't realise that the pizza shops and estate agents drowning their doorsteps with junk mail are able to do so because their local council is forced to sell the names of every voter who fails to tick the right box when they register to vote.
"The edited register is a pointless waste of council time, undermines trust in the electoral system and contributes to huge volumes of junk mail. It should be abolished."
According to Freedom of Information Act requests, councils sold the edited electoral register - made of up all those people who register to vote and do not opt-out of the edited version - to pizza shops, estate agents, lobbyists and driving schools among others.
The group calls on the Government to abolish the edited register or allow councils to offer people a permanent opt-out instead of the current system that requires people to opt out annually.
Some 307 local authorities sold the edited electoral register to more than 2,700 different companies and individuals between 2007 and 2012.
A breakdown of the findings shows there have been at least 2,742 sales of the edited register over the five-year period, raking in at least £265,161.21 for the local authorities.
The council with the most buyers was Westminster, which sold it 93 times, while three other councils - Elmbridge, Kensington and Chelsea and Broadland - sold the edited register to more than 50 buyers.
Big Brother Watch said if the edited electoral register is to be retained, the Cabinet Office should allow councils to include a permanent opt-out option on the electoral registration form, something currently not possible due to statutory provisions.
A spokesman for the Department for Communities and Local Government said: "It is completely unacceptable for councils to be profiting in this way.
"Junk mail is a menace and councils should be looking at ways to make sensible savings and not taking advantage of voters."