New rules aimed at clamping down on nuisance "silent calls" from telesales firms have been launched.
Householders object to being interrupted by cold callers
The Direct Marketing Association (DMA) has brought in new guidelines after research showed such calls made 22% of people anxious.
Telemarketers must now give a phone number to the person called. Calls to that number must be free and give the name of the organisation calling.
Members of the trade association have three months to comply with the rules.
The DMA will also be setting up a database listing the free call-back numbers and the names of the companies using them.
Members of the marketing and communications industry trade association must also have measures in place to deal with "do not call" requests from consumers.
Cold calls have prompted more than eight million people to sign up with the Telephone Preference Service, which screens all sales and marketing calls.
"The DMA are trying to take the lead on this issue," a spokeswoman for the group said. "Ofcom welcomed the research and we will be working with them on joint initiatives to tackle this issue."
Of the 1,000 people quizzed for the DMA survey, 37% said the calls were an "unacceptable inconvenience".
Phone owners got an average 5.7 nuisance calls a month. However, among the over-65 age group the average number of silent calls rose to 7.3 per month, possibly because they spend more time at home.
"Silent calls" are often generated by automatic dialling machines.
Industry regulator Ofcom found such calls are often made by machines in call centres, which hope to drum up new custom by cold calling customers - when a number connects it is routed to an operator.
If no operator is available the connection is terminated, leading to the "silent call".
Ofcom added that the three main culprits for such calls are telemarketing firms, financial services and number scanners that dial sequences of numbers to find which ones are active.