Firms selling anything from double glazing to insurance have 28 days to clean their call lists of people who have registered with the Telephone Preference Service.
Colin Lloyd, chief executive of the Direct Marketing Association, which is running the register, said hundreds of firms had contacted the association to ensure that they were complying with the rules. He was hopeful that the regulations would help to clean up the image of telemarketing as well as save businesses money.
"The introduction of the new regulations has real benefits to businesses as it will ensure they don't waste time or money calling consumers who just don't want to be bothered," he said.
"Every wasted call costs UK firms about pounds 2.50 and, given the size of the telemarketing business, that means potentially massive savings. The response over the last four weeks has been tremendous."
The UK's telemarketing industry has grown substantially in recent years. About 75 per cent of companies with more than 100 staff now use the telephone to keep in contact with customers and try to sell them new products and services. The industry employs some 1.3m people - 5 per cent of the national workforce.
Companies are developing sophisticated and personalised strategies to sell by telephone. According to the Henley Centre, in the six months to March 1998, companies made 41m calls to potential customers, although nearly half were "warm" calls, made by organisations that already had a commercial relationship with the individual.
The research showed that companies can exploit the use of telesales further. Consumers use the phone more and more to buy goods and services, and nearly three-quarters of adults say it is acceptable for a company to call them at home if they have bought something from that company before.
There are now 7,000 call centres in Britain, but few of them are geared to the new teleculture, according to the research. The focus is on cutting costs, with telesales workers timed as they make scripted calls, rather than generating revenue by building relationships with customers.
In the past the system of firms removing numbers from their lists if requested was voluntary and self-regulated by the direct marketing industry.
But so-called "junk calling" has resulted in so many complaints that the telephone industry watchdog, Oftel, is now backing the new legal enforcement of the scheme.
Those wishing to register with the Telephone Preference Service should call: 0845 070 0707.Reuse content