Signing up to the Telephone Preference Service will only cut spam calls by around a third but reduces other kinds of nuisance calls too.
Communications regulator Ofcom found being on TPS reduced the average volume of sales calls by 31 per cent, and all types of nuisance calls fell by 35 per cent.
With many unscrupulous companies ready to flout the rules, the TPS called for the government to increase the official watchdog’s powers to investigate and punish nuisance callers.
John Mitchison, the head of the TPS, said: “TPS is the only official ‘do not call’ list; by law companies cannot call people registered with TPS for sales and marketing purposes, unless they have prior permission to do so.
“Ofcom’s findings show that TPS is effective at stopping live sales calls from companies that comply with the rules.”
Nearly half of people who register with TPS (45 per cent) had not received any live sales calls, compared to a quarter (26 per cent) of of those who weren’t registered.
Other types of nuisance calls affected by signing up to TPS included recorded marketing messages, and silent and abandoned calls – often left by auto-diallers which want to leave a message on an answering machine.
Nuisance calls and texts are investigated by the Information Commissioner’s Office (ICO), which can take companies to court and levy fines of up to £500,000.
The problem, says Mitchison, is proving a company’s responsibility for making nuisance calls and texts.
“TPS cannot stop all nuisance calls,” he added. “Currently, the high burden of proof required makes it extremely difficult for the ICO to impose fines that stick.
“TPS supports the industry’s calls on government for legislative changes that will make it easier for the ICO to issue financial penalties to companies flouting the rules. A swift response from government will increase people’s confidence in the current system that’s there to protect them.”
The ICO has so far levied fines on five companies: DM Design (£90,000), Nationwide Energy Services (£125,000), We Claim You Gain (£100,000), Tameside Energy Services (£45,000) and Amber Windows (£50,000).
From October 2014, new rules will allow Ofcom to share information with the ICO to help it investigate nuisance callers.
Claudio Pollack, Ofcom’s Consumer Group Director, said: “It’s encouraging that people who register with the Telephone Preference Service see a significant reduction in nuisance calls.
“But we understand how frustrating it is to still receive some unsolicited sales calls despite being TPS-registered. That’s why we welcome tough enforcement action from the ICO against rogue companies who breach the rules as part of regulators’ joint work to help tackle nuisance calls.”
The government is also consulting on changes to the law which may give the ICO more powers and change the rules on marketing consent to help people to opt out.
Simon Entwisle, the ICO’s Deputy Chief Executive, said: “While the results of this research show a decrease in the number of nuisance calls received by people registered with the TPS, it also shows that too many people continue to receive them. This is why there must be no further delay in strengthening our powers.
“Nuisance calls are just that – ‘a nuisance’ – and we believe that should be sufficient to let us consider a fine.”