The first directory service that claims to be able to find any British mobile phone number is expected to cause a row over privacy when it begins operation next week.

For a £1 charge, 118800.co.uk will be able to connect customers of its service to any of Britain’s 42 million mobile phones, it says.

The directory, which goes live on June 18 and already contains “millions” of mobile numbers and their users, is the first of its kind in the UK. It will function along the lines of an old-fashioned telephone operator: users will call the service and ask to be connected to the mobile phone of a person. The service calls that mobile phone and asks for permission to connect the call.

The service has been developed using data bought from market research businesses. People not wishing to be included on the list must inform the directory by text or phone that they wish to opt out. They will be charged their standard network rate and face a wait of four weeks before their number is excluded.

Though the company says that its policy is not to include under-18s on the directory, where parents have given their children mobile phones they will also need to text from the children’s phone to exclude them.

Connectivity, the company behind the service, insisted yesterday that “users’ privacy is paramount”. It stressed that none of the numbers or personal details on its directory would ever be divulged and callers will be connected to the number they request only if the call receiver agrees.

It said it had worked closely with consumer bodies such as the Office of the Information Commissioner (ICO) during the development of the service.

The ICO confirmed that it had held discussions with the group but warned the service would need to implement its suggestions and obtain consent from the individuals involved to comply with the Data Protection Act.

However, privacy groups said that it would provoke serious anger from people concerned about having their private lives invaded. Simon Davies, of Privacy International, who worked on the project as a paid consultant during its early phase, said: “There are fundamental privacy issues. The company needs to be far more specific about where it acquired the numbers on its directory and from what sources.”

While people on the directory must have, at some stage, agreed to have their number circulated, many would have unwittingly done so, he said, by failing to tick a box on a market research form, for example. Many would be alarmed to discover that they now featured on a national mobile phone database. “The dynamics of disclosure with mobile phones is radically different from landlines,” he added. “People tend to enjoy selective disclosure with their mobile phones.”

There is also a danger that marketing companies and businesses could abuse the service to get hold of potential customers, providing a further route of annoying spam.

Connectivity said that its data “generally comes from companies who collect mobile telephone numbers from customers in the course of doing business and have been given permission by customers to share those numbers.” Although mobile phone operators keep personal details of contract customers, their information is sullied because the person registered with the phone might not be the user.

Connectivity, whose service is being tested online before its launch as both an internet and phone service, initially planned to seek the permission of all mobile phone users on its list by contacting them. It then decided it was more “relevant” for people to choose to opt in or out when someone first tried to get hold of them. Far from being angry, the company believes that many people will want to participate in a service.

It wants mobile phone users to sign up by detailing their number and home and workplace details on its website. If the requested user fails to answer, the service will leave a message with the contact details of the person seeking to speak to them.

Shona Forster, Connectivity’s marketing director, said: “The person whose number it is is always in control. Their privacy is of paramount importance to us.”

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