It said it the companies warned have failed to comply with informal requests, so it has decided to change its approach from negotiation to enforcement. It is also investigating other cases and may issue warnings to more companies.
It has sent out preliminary notices indicating its intention to serve a enforcement notice requiring the companies to comply with Regulation 21 of the Privacy and Electronic Communications Regulations by ceasing marketing calls to people who have asked the company to stop calling them and/or who are registered with the TPS.
If a company fails to comply with an enforcement notice, the ICO is able to prosecute.
The warnings were served in August to seven companies: Toucan; Carphone Warehouse and its fixed-line sister company Talk Talk; and four home improvements companies trading from the same address -- Bowater Home Improvements, Bowater Windows, Staybrite Windows and Zenith Windows.
In the year to July, the ICO received: 67 complaints about Toucan; 46 about Carphone Warehouse and Talk Talk; and 31 about the Bowater group.
The ICO said it has received responses from the companies and is now considering its next steps.
A spokesman for Carphone Warehouse told Brand Republic: "TalkTalk fully adheres to the Data Protection Act and makes every attempt to screen all marketing calls against the Telephone Preference Service mailing list. We are working closely with the ICO with their enquiries."
Toucan Telecom has just changed hands from IDT to broadband operator Pipex, with the sale completing yesterday.
There have been 39,941 complaints made to the TPS between the start of this year and the end of September, compared with 54,380 in the whole of 2005. As of August 2006, there were 13.3m phone numbers registered with the TPS.
In reaction to the ICO's action Richard Webster, the Telemarketing Association's chairman, said: "It may be that the companies cited feel that they were legitimately allowed to phone these individuals (even though registered on TPS) because they were their customers or prospects.
"I would point out that as often happens, the easy targets are chosen rather than the hardened offenders, by which I mean that in this case, legitimate British companies can easily have enforcement notices served. Those responsible for the huge volume of calls to TPS numbers made from overseas remain untouchable."
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