Guidance on the blocking of international inbound calls has been drawn up at Ofcom’s request by NICC, the UK telecoms standards body which represents major networks including 02, TalkTalk and Virgin.

It comes after Ofcom discovered that scammers targeted nearly 45 million people with fraudulent texts and calls over the summer.

Landline users were being plagued with fraudulent calls, with 61pc of people aged 75 and over reported receiving a potential scam call to their house phone.

Priti Patel, the Home Secretary, this week announced a Joint Fraud Taskforce to tackle the “devastating impact” of a 24pc overall rise in fraud during the Covid pandemic.

In the United States, the Federal Communications Commission (FCC) this month announced plans to force phone companies to block millions of scam texts.

However Whitehall sources insisted the approach would not work in this country because much of the UK network still relies on copper-based ISDN technology.

Ofcom is now “encouraging” UK companies to accelerate the move to internet-based VOIP, which allows scam texts to be more easily detected and blocked.

Phone networks are already using artificial intelligence to spot scam texts and block the numbers responsible.

Regulators are also examining whether customers should be forced to show their ID when buying multiple SIM cards, often used by scammers to send millions of scam text messages.

However Ofcom is understood to have concerns that doing so would “marginalise” vulnerable groups who may not possess identification.

“There is no single answer to how to stop scam texts, unfortunately,” one senior source said.

“It’s rather like whack a mole because the scammers can adapt so quickly to everything we try to do.”