The telecoms giant revealed it will analyse and identify rogue numbers which will be diverted to a junk voicemail box, before it reaches a customers’ landline.

Currently customers can buy a BT nuisance call blocker phone and they’ll need to add the monthly paid-for privacy and caller display option to their calling plans.

It comes as recent research by Which? shows that 75% of customers receive unwanted calls each month and BT is now also calling on other companies to join the fight against nuisance companies.

However, TalkTalk which already diverts 70 million unwanted calls a month, said this urgent problem can only be tackled if the government mandates all telecoms providers to offer free call blocking.

How will the BT blacklist work?

BT says the free service – due to launch towards the end of this year – will be achieved by “harnessing huge computing power” to analyse large amounts of live data. Its network experts will then identify the rogue numbers, such as those that make an enormous number of calls, and add it to the blacklist.

The provider said the blacklist will be expanded if large numbers of customers identify troublesome numbers they wish to divert.

It added customers will also be able to compile their own personal blacklist by adding individual unwanted numbers and by noting whole categories of calls they want to avoid, such as international calls or withheld numbers. BT will then prevent these types of calls from reaching customer handsets and it will also share the information with telecoms regulator, Ofcom, as well as the Information Commissioner’s Office.

Removing major hassle and grief for millions

John Petter, chief executive of BT consumer, said: “Nuisance calls are one of the great annoyances of modern life. We are delighted to have made this major breakthrough. We are giving control of the landline back to our customers and removing a major hassle and grief for millions of customers.

“We are doing our bit. We call on other providers to up their game in the fight against this menace. They can help us to root out the malicious players they may be hosting on their own networks when we identify dodgy and suspicious calling behaviour.”