A Government-regulated service intended to allow people to block cold callers is being ignored by some telemarketing companies, a Panorama investigation has claimed.
The BBC Current affairs programme found that despite thousands of complaints from the public being lodged with the Information Commissioner each month, there have not been any fines imposed on offending companies for at least 18 months.
Around 17.5 million phone numbers are registered with the Telephone Preference Service (TPS) - a scheme designed to prevent UK-based companies from making unwanted cold calls.
Industry rules say telemarketing firms should crosscheck their database to ensure that people who have asked not to be cold called are left in peace. But Mike Lordan at the Direct Marketing Association, which runs the TPS, told Panorama that some companies are ignoring the rules.
He said: "Companies are not abiding by legislation and we should be seeing enforcement against those companies who are persistently breaching legislation."
Richard Lloyd from Which? Magazine also told the programme: "Even if you have signed up to the telephone preference service now, it won't make a jot of difference to those companies that are buying and selling that information you gave to that website maybe years ago."
One of Panorama's undercover reporters secretly filmed staff at Central Claims Group, based in Bury, Greater Manchester, allegedly tearing pages out of the phone book and calling people at random.
In a statement to Panorama, Central Claims Group said it takes its legal and regulatory obligations very seriously and does not condone the lapses Panorama filmed.
It said they "have informed all employees that using the ordinary telephone directory or introducing themselves as anything other than Central Claims Group will be regarded as gross misconduct warranting summary dismissal".
A spokesman for the Information Commissioner's office said that until this year, they did not have suitable legal powers to act. Although they now have the power to impose fines of up to £500,000, they say that enforcing the rules is not easy given the vast amounts of money that companies which flout the rules stand to make.