Telecoms regulator Ofcom is to review the cost of calling telephone services such as directory enquiries.
According to the watchdog, the amount being spent by consumers on mobile and landline calls has come down in recent years, while people have a wider choice of call packages and phone services.
Nevertheless, Ofcom believes that the cost of calling some telephone service numbers is going up, in particular directory enquiries numbers starting with 118 and 'personal' or 'follow-me' numbers that begin with 070.
The watchdog is carrying out its review to ensure consumers are protected from unfair practices and that the prices are transparent.
"Our Call Cost Review will consider whether consumer harm is arising out of deliberate misconduct or market failure, and what action may be required," Ofcom said.
"We expect to publish detailed proposals later this year. We are also talking to the Phone-paid Services Authority about whether there are any additional consumer protection measures it could consider under its Code of Practice."
More than 500 directory enquiry services offering various options and prices are now available, with call costs varying from 35p per call to £9 and above.
Ofcom said it has been closely looking at the costs of the more expensive services, as prices have gone up "significantly" in the last few months because fewer people are using them.
The regulator's concerns about 070 numbers stem from the fact they might be confused with mobile phone numbers, which start with the same two opening digits.
Ofcom believes there is evidence of scams designed to trick people into believing they are calling a mobile number, when in fact they are calling a service that costs up to £3.40 per minute.