The police warned recently of a convincing new “friends in need” scam targeting parents.

Victims of the scam receive a WhatsApp message from a random number purporting to be from a son or daughter who has lost their phone. Once parents are convinced they are speaking to their child, scammers ask them to send money to cover an imminent payment coming out of their accounts.

Santander said it had received an increasing number of reports about the con, with case numbers doubling month on month since August and several hundred customers reporting being targeted. Victims have already lost tens of thousands of pounds to the emerging “hello Mum” and “hello Dad” fraud, according to Action Fraud, the scams arm of the police.

WhatsApp declined to say how many accounts suspected of perpetrating the scam it had deleted, but said it used “advanced machine learning” to ban millions every month for spam or abuse.

The messaging app’s Kathryn Harnett said users should never divulge their six-digit login codes “even to friends or family” and said “calling or requesting a voice note is the fastest and simplest way to check someone is who they say they are”. 

“A friend in need is a friend worth calling,” she added.

There were almost 19,000 recorded cases of impersonation scams, where fraudsters posed as bank staff, police officers or NHS employees, in the first six months of 2021.

More than £750m was lost to the fraud in the first six months of the year, with scams up almost a third on the same period last year, according to the banking trade body UK Finance.