Many consumers mistakenly believe that when dialling on 070 number, they’re calling a mobile phone.

But calling these numbers often leaves consumers with ‘bill shock’ as phone providers charge between 45p and £1.10p a minute to call these numbers.

According to the regulator, Ofcom, there were 2.6 million calls to 070 numbers last year, which allow calls to be diverted from one number to another to keep the recipient’s number private.

Small businesses and sole traders also use them to make it easy to manage calls, and classified adverts often use these prefixes instead of someone’s personal number.

But the watchdog said as well as being confusing and expensive for consumers, these numbers are also being used to defraud people.

It found evidence of scams, such as missed calls and fake job adverts which take advantage of consumers’ lack of awareness surrounding the high costs of calling 070 numbers. It estimated that a minimum 20% of 070 calls involve some form of fraudulent activity.

As such, Ofcom will introduce a 0.5p per minute price cap to call 070 numbers and such a move should also mean that phone providers can include these in free minute allowances.

Jonathan Oxley, Ofcom’s competition group director, said: “Millions of calls are made to 070 numbers, but many people aren’t aware of the high costs of calling them. This can lead to people receiving much higher bills than expected.

“So we’re slashing the wholesale cost of connecting 070 numbers. There’s no reason why phone companies shouldn’t pass this saving on to their customers as soon as possible.”

Ofcom confirmed there will be a 12-month implementation period to give businesses time to make the necessary changes.