Ofcom has announced it is reviewing landline rental prices, following recent increases in line rental charges.
According to the telecoms regulator, charges have risen by between 28 per cent and 41 per cent in real terms over the last few years.
This, it said, is despite the fact the underlying wholesale cost of providing landline services has fallen by about a quarter.
The watchdog is therefore concerned that consumers, in particular standalone landline customers, might not be getting value for money.
Jonathan Oxley, Ofcom’s Competition Group Director, commented: "We’re particularly concerned for older and vulnerable customers, who rely on their landline and are less likely to change provider.
"So we’re reviewing this market to ensure these customers are protected and getting value for money.”
Ofcom pointed out that standalone landline customers do not have broadband or a pay-TV service and therefore do not benefit from the competition in the market for packages where these services are bundled together.
The watchdog said elderly and vulnerable people account for a significant proportion of this group and are particularly affected by price rises.
"They are often very reliant on their landline and more likely than most to have stayed with the same phone company all their life," Ofcom stated.
The watchdog added that the review is necessary because recent changes requiring broadband providers to be clearer about line rental costs will not benefit landline-only customers
In October, the Advertising Standards Authority (ASA) introduced rules stating that broadband providers must offer all-inclusive pricing, with line rental and broadband costs being shown as a single figure.
The organisation hopes this will prevent people feeling misled by advertising claims and paying more than they expected for an internet connection.
Richard Neudegg, Head of Regulation at uSwitch.com, commented: "Landlines are a lifeline, but for those who don't want broadband - often the most vulnerable - the prospect of ever-increasing line rental charges still looms.
"The ASA's reforms to require all-in costs for landline and broadband services should help matters by putting more competitive pressure on the providers. They now have greater incentive to compete on line rental as well as broadband pricing to make their combined costs appear more attractive.
"Reviewing landline-only pricing with its competition hat on will be seen as a bold move by Ofcom, but it's a necessary one to ensure the most vulnerable are getting a fair deal.
"In addition to Ofcom's review of line rental pricing, we would like to see the regulator take a close look at whether BT Basic is fit for purpose for vulnerable, elderly and low-income households.
"Ofcom currently requires BT to provide BT Basic - the telecoms equivalent of the Warm Home Discount for energy – as a condition of its historic monopoly.
"However, customers would only have to use their landlines for 148 minutes a month for a standard landline tariff to be more affordable than BT Basic."