Each household is to be questioned on its lifestyle from finances, health problems and reading habits down to its favourite ketchup, in the most ambitious survey carried out by a private company. ICD Marketing, one of the biggest list brokers in Britain, plans to send out the questionnaires in the autumn. The detailed information will be sold on to companies at a starting price of pounds 80 for every 1,000 names.
It will include precise information on the buying habits of individuals across Britain.
Lionel Thain, chief executive of ICD, said: "It was always the cliche of junk marketing, when the lawnmower manufacturer would send a mail to everyone in the road, even though houses had been converted into flats, and it was only the man on the ground floor who might be interested."
ICD has already questioned half of Britain for previous surveys, and their advertisements boasted "the list is endless". It included the offer of names and addresses of 75,311 haemorrhoid sufferers, 59,474 women who have problems with tight shoes and 30,561 people who watch Tomorrow's World.
The Advertising Standards Authority, which is partly responsible for monitoring the flow of information into databases, said its supported the move, as long as individuals who filled in questionnaires were aware how information would be used. A spokesman said: "It could benefit consumers. They are trying to improve targeting, as part of the direct mail industry's attempt to rid itself of this 'junk mail' label. If you receive something that is of interest to you, it clearly ceases to be junk."
However, there is mounting concern over how much is known about individuals in Britain. Information from credit searches, the electoral roll and loan companies fills up databases, and details are used by political parties and charities as well as companies.
The Government is currently considering allowing personal information about benefits claimants to be sold to private companies; and there is some unease over the Labour Party's new database, Excalibur, which contains information on the voting patterns of millions of Britons.
The marketing questionnaires are filled in voluntarily, and members of more than 12 million households have completed them, often with the incentive of a prize draw for a free holiday or video camera.
They are monitored by the Data Protection Registrar, which has legal powers to enforce companies to clarify how the information will be used.
David Smith, assistant registrar, said: "We require the information is fairly obtained. The most important thing is that people know what they're letting themselves in for when they fill in these very personal questions."
Any irritated recipients can write to the Mailing Preference Service and ask to have their names taken off lists. About 400,000 people have already done so; they alone can be sure of not receiving a questionnaire from ICD.