The opt-in service means UK customers can stop calls from Payment Protection Insurance sellers or nuisance calls from ever reaching their phone.
The operator has yet to launch the service for its mobile arm EE, but according to director of voice and multimedia Tim Shaw, that option will be launched within the next year.
Speaking exclusively to Capacity at the launch of the service at BT Tower, London, Shaw said: ““The uniqueness of our solution is both the network intelligence and linking it with the crowd-sourcing piece. Previous solutions have been either on the network or a home-based solution, but our application combines that.
“As you make the call, it goes through our switches and pings our application server. There our system decides what to do with that number. If it is on the blacklist, it forwards the call to the spam voicemail inbox.
“We’ve all experienced nuisance calls, and they are annoying. From a customer service standpoint, if we can hand customers the tools to block these calls themselves, then they will really benefit from it.
“From a network point of view, it takes a large number of calls off the network, which means we’re not flooding certain switches. Sometimes these companies attack in a geographic way, which is a concern.
“We’re working on how we can take this technology into our mobile network and we expect to launch that within a year or so.”
The service uses an algorithm designed by BT to assess call behaviour and phone numbers to develop a blacklist of potential spam callers. These are then automatically blocked from reaching customers who opt-in to the service, although they can be listened to through a “junk call” voicemail folder.
Customers will also be given the option to block numbers they don’t want to receive calls from using an online portal or automated phone service.
BT estimates up to 30 million nuisance calls a week could be diverted using the service, which it has labelled Call Protect. On average, UK landline owners receive four nuisance calls a week, with 60% deemed stressful by the recipients.
The service has the backing of both regulator Ofcom and the Department for Culture, Media and Sport. BT said it will also work with the Information Commissioners Office to pass over any information of any companies found breaching telemarketing laws.
Matt Hancock, digital and culture minister, said: “Nuisance callers are a terrible blight on society and Government and industry are working together to crack down on them. We’ve forced companies to display their numbers when they call you, made it easier to prosecute those involved in making the calls, and increased the maximum fines up to £500,000.
"We welcome BT's new service, which offers customers an additional level of protection, helping them to fight back against this ongoing harassment."