By Jane Dreaper
BBC News health correspondent
A ban on the use, by GP surgeries and other parts of the NHS, of phone numbers which begin with 084 is being considered, say ministers.
They have launched an England-wide consultation to ask people whether they want to keep the numbers.
Doctors say the new systems enable them to offer patients a better service.
But campaigners argue using the more expensive numbers is against the founding principles of the NHS, which should be "free at the point of need".
Increasing numbers of GP surgeries, hospitals and primary care trusts now have 084 numbers for patients' use, such as when booking appointments.
Dr Richard Vautrey says his patients get a better service
Callers to the numbers are put in a queue, rather than encountering a constantly engaged tone.
Any revenue that is raised has to go towards the cost of the phone systems.
However complaints over the use of the numbers - which are usually more expensive than local calls - have led to a government rethink.
In theory the numbers should cost about 5p a minute, but they tend not to be included in calls packages which people often have on their landlines.
For people using a mobile, the additional charge can be as high as 40p per minute.
Over the next three months people in England will be able to give their views on whether the practice should be allowed to continue.
The NEG (Network Group Europe) company, which supplies 084 numbers to the NHS, says 10 million patients across the UK are registered with a doctors' practice that uses the system.
One such surgery is the Meanwood Practice in Leeds, where Dr Richard Vautrey is based.
Dr Vautrey, deputy chair of the British Medical Association's GP Committee, said: "Before we put in the system, patients were concerned about the difficulty they had in getting through on the phone.
"Surveys showed it was an area of weakness for us.
"It's never going to be perfect but the 084 number has given us a dramatic improvement and certainly made a big difference.
"Any idea that GPs make money from these numbers is a myth.
"The cost to our practice has in fact increased since we put in the new system.
"Before it was £7,000 a year and now it's £10,000."
But phone campaigner David Hickson said the use of the numbers was "completely unacceptable."
He said: "The NHS is supposed to be free at the point of need.
"The difference in each call may be only a few pence for some people, but the costs can really mount up for others - especially for people who are using mobiles because they don't have a landline.
"I find it bizarre that the government is doing a consultation on this now.
"It's more than three years since the Department of Health banned GPs from using 0870 and other higher cost numbers. 084 numbers should have been stopped then."
One solution could be to use 03 numbers across the NHS. These offer the extra functions of automated 084 systems, but without patients having to pay extra.
However some GP surgeries are locked into phone contracts lasting as long as seven years.
HAVE YOUR SAY
If the NHS wants to save money it should cut GPs salaries not charge over the odds for phone calls
Bert, Salisbury, UK
Health Minister Ben Bradshaw said: "A few years ago we banned the previous systems that were proving expensive.
"But people got round it by using 084 numbers. We now need to find a sustainable solution.
"We'd have to look carefully at whether existing contracts could be interrupted."
Mr Bradshaw confirmed that the consultation would also seek the public's view about the phone line service NHS Direct using an 0845 number.
Dean Raiment, the managing director of NEG, said: "We also share the government's determination that patients all over the country should receive the best possible service.
"We look forward very much to continuing to work with the Department of Health as part of the consultation process, to determine the most appropriate solution."