Carphone Warehouse subsidiary, Talk Talk, broke data protection law by making unwanted sales calls to consumers, the State's communications watchdog said yesterday.

ComReg and the Data Protection Commissioner recently ordered the telecom group's Talk Talk operation to halt sales activities and apologise publicly after receiving complaints from the public about unwanted calls from the company.

Talk Talk sells fixed-line services to consumers. Staff at an outside sales agency hired by the company had been making unsolicited or "cold" calls to consumers.

But a number of those people its agent called had previously registered on a database of people who do not want to be contacted in such a way.

Communications regulator ComReg said in a statement yesterday that it was an offence under the 2003 Data Protection Act to cold call people when they have registered on this database. The regulator said that it had censured Talk Talk over the activity.

The consumers complained to ComReg and to the Data Protection Commissioner, which polices the way in which organisations maintain and use information about individuals.

The Data Protection Commissioner can take prosecutions under data protection legislation.

In its public apology, Talk Talk blamed the problem on the agency's "internal processes".

Carphone Warehouse chief executive Stephen Mackarel said yesterday that the issue came to light about three weeks ago, when consumers complained to the two regulators.

Mr Mackarel said the company stopped its sales activities until the faults had been rectified.

In its apology, Talk Talk said that the faults "resulted in us inadvertently contacting some consumers who have previously registered a preference to be recorded on the national directory database as not wishing to be contacted through telemarketing calls".

It stated that the company "sincerely" apologised to those who received unwanted cold calls from Talk Talk.

Mr Mackarel said that the problem dated back to the systems set up by Tele2, the fixed-line operator that Carphone Warehouse bought last December.

It was rebranded as Talk Talk after the deal was completed earlier this year.

"We inherited their systems and there were a number of gaps in them," he said. "We immediately took all the necessary remedial action when we heard about the complaints."

ComReg said it received 20 complaints about unwanted cold calls from the company. However, Mr Mackarel said the number was four.

The regulator said yesterday that while it supported competition, all operators had to comply with their obligations.

This is the second case of unwanted cold calling that the regulator has investigated in recent months.

Consumers can register to opt out of getting unwanted cold calls through ComReg's website.