Remotely monitoring patients with long-term conditions is less cost effective than usual care, a UK trial suggests.
The British Medical Journal study, involving almost 1,000 patients, indicated the total costs for those using "tele-health" were higher.
It follows a recent study suggesting the use of such technology fails to improve patients' quality of life.
But the Department of Health said it had already addressed problems raised by the research.
Tele-health uses technology in patients' homes to monitor their condition and send data back to medical staff. For example, tracking changes in blood pressure or blood-sugar levels.
The principle is that it reduces the need for hospital visits while allowing clinicians to keep an eye on a patient's condition.
But the researchers said most of the previous studies into the technology's use came from the US, used very small numbers of patients or were funded by industry.
Counting the cost
In the latest Department of Health funded trial, researchers looked at 965 patients with heart failure, chronic obstructive pulmonary disease or diabetes.
They were selected for the trial by their GP and received either usual care or were provided with tele-health equipment.
After a year, the researchers found that taking into account all costs, including those to both health and social care, the tele-health scheme was not cost-effective.
The cost per quality-adjusted life year - a combined measure of quantity and quality of life - of tele-health was £92,000 when added to usual care.
This is way above the threshold of £30,000 that the National Institute for Health and Clinical Excellence has set.
A best-case scenario taking into account that the price of equipment was likely to fall over time and that services were not running at full capacity during the trial, saw the probability that the service was cost-effective rise from 11% to 61%.
The government has been keen to promote tele-health as a way for the NHS to cope with an ageing population with multiple long-term conditions.
Initial results from the Whole System Demonstrator trial of the technology seemed very positive, with fewer admissions to hospital.
But recently, more work from the trial showed no measurable benefit to quality of life, and the latest work suggests that claims tele-health will produce dramatic savings for the NHS were premature.
Study author Prof Martin Knapp, from the London School of Economics and Political Science, said there was likely to be a place for tele-health, but there remained a question about how to target patients who would most benefit.
"We need to use the evidence to give us an indication of who does better. It is about how we use it and what it is we are using."
He added: "Some patients do not want to lose that face-to-face contact."
Dr Mike Knapton, associate medical director at the British Heart Foundation (BHF), said: "Tele-health and tele-monitoring could potentially improve the quality of life for patients living with long-term conditions such as heart failure.
"However... in the current financial climate, it is difficult to see how healthcare commissioners could justify investment in tele-health on the basis of this research."
Cathy Moulton, Diabetes UK clinical adviser, said detailed research was needed on the impact of tele-health on diabetes as a stand-alone condition to see if any savings were possible.
"While tele-health may suit some people with diabetes, it is extremely important that everyone with diabetes has access to individualised care which is tailored to their specific needs."
The Department of Health said: "This is only one part of a much wider study carried out between 2008 and 2010.
"The whole study showed that using tele-health reduces mortality by 45%, A&E attendances by 15% and emergency admissions by 20%.
"This part of the study confirms that to introduce the technology in isolation, at high cost and in low numbers does not bring the cost reductions we believe are there to be made.
"That is why our approach, known as the three million lives initiative, is different. It is about bringing in tele-health at scale and will create improvements in services, care and costs."