Callers would save money if government helplines switched to 03-prefixed numbers, Ofcom said.
Shocking figures have been released by the National Audit Office revealing the huge cost of calls to government offices since the introduction of Non-Geographic numbers – 0845 numbers
Callers waiting to ring HMRC spent £136m on call costs last year and higher rate government phone lines cost callers £56m last year, the National Audit Office has revealed.
Those most likely to be affected are those on low incomes who are more likely to use pay-as-you-go mobiles, it said.
About one third of central government helplines incur higher-rate charges but account for 63% of the calls made to government, the National Audit Office (NAO) said.
Average landline call costs to standard geographic numbers and those that begin 03 cost around 3.4p per minute and 1.1p from mobile phones, this rises to 5.6p from landlines for 0844 numbers - and 17.1p from a mobile phone.
The sample also found that 4% of local authority phone lines and 8% of GP surgeries were using 084 numbers. The NAO estimated that the value of callers' waiting time was about £100m.
NAO head Amyas Morse said: "Callers do not receive a better service from higher rate numbers and many callers are put off calling government phone numbers altogether. The most vulnerable callers, such as low-income households, face some of the highest charges.
"Call charges are complicated and difficult for callers to understand. Charges to higher rate numbers are greatest from pay-as-you-go mobile phones, relied on heavily by low income and vulnerable households. In its proposed reforms, Ofcom needs to get to grips with this confusing charging system.
Higher rate telephone numbers across central government cost callers an eye-watering £56m in 2012-13. The Cabinet Office needs to step up and set guidance for departments so they can focus on minimising the costs of providing telephone lines for the taxpayer and user.
A spokesman for communications watchdog Ofcom said: "Ofcom has announced detailed plans to make the charging system much clearer for all non-geographic numbers, such as those beginning 08. We expect to finalise those measures in the autumn.
"We also actively encourage public bodies to use 03 numbers, as these cost no more to call than a normal geographic number."
A spokeswoman for the Cabinet Office said: "The Government Digital Strategy sets out how government will re-design its digital services to make them so straightforward and convenient that all those who can use them will choose to do so, whilst assisted digital support is being developed so that those who cannot are not excluded, protecting vulnerable groups in particular.
"In the past, government has not been joined up in reviewing the use of paid-for numbers, so a more coordinated approach is required. Where possible, we should use government's unique buying power to negotiate the best deal for the taxpayer.
For more information about Non-Geographic numbers please contact Merlin Telecom on 0800 877 8810.
Reference: BBC News.