Telecoms regulator Ofcom lobbied for the change, which has been put forward by the Department for Business and Skills for Parliamentary approval.

Ofcom says the vast majority of silent calls are caused by automated diallers. These devices are commonly used for telemarketing activities, but they are also used in large-scale telephone survey recruitment. Silent calls are generated when the diallers make calls to more numbers than can be answered by staff.

Rules state that the number of silent calls generated by a call centre must not exceed more than 3% of the total call volume each day and that when a silent call is generated a recorded information message should kick in two seconds after the homeowner answers the call.

The Market Research Society has published its own regulations for using auto-diallers in research, available for download here.