A service that aims to block millions of nuisance calls each year before they reach Scottish homes is being launched by BT.

The Call Protect service is under the charge of a team at BT's Oswestry, Shropshire centre, who analyse live data to identify rogue numbers - typically those that make enormous numbers of calls - and add them to a blacklist.

The service, available for BT customers to opt into for free, diverts calls before they reach homes, unlike reactive blocking which has been hampered by nuisance callers frequently changing their numbers to avoid detection.

BT estimates that the service could divert up to 30 million calls a week across the UK, including up to 15 million from personal accident claims and PPI companies alone.

Users will also be able to compile their own personal blacklist by adding individual unwanted numbers by dialling 1572 after receiving the call or by going online.

Nuisance callers identified by large numbers of customers will also be added to the list.

A survey for BT found that people in Scotland receive an average of four to five nuisance calls a week, and 60% of people in the UK find them stressful.

Brendan Dick, BT Scotland director, said: "This new service is great news for people in Scotland. We know that nuisance calls are a big problem for people in Scotland, who receive many millions of such calls every year.

"Some of these calls can be upsetting and unnerving as well as very annoying, particularly for people who are more vulnerable perhaps through age or disability. We take this issue very seriously and, as this important new service demonstrates, are determined to do everything we can to help our customers beat the problem."

John Petter, chief executive of BT Consumer, said: "We're declaring war on the companies that regularly pester our customers with nuisance calls on subjects such as PPI and personal accident claims. We're giving our customers the means to fight back against the millions of unwanted calls for free."

UK Digital Minister Matt Hancock has welcomed the new service.