Elderly and vulnerable patients will be hardest hit by a decision to more than double the cost of telephone calls from hospital beds, according to patients' groups.

Patientline, the company which charges people to make phone calls and watch television in hospital, is increasing bedside call charges by 160%, - from 10p a minute to 26p.

For people calling patients from outside hospital, the cost is already 39p per minute off-peak and 49p a minute at peak times. Shares in the company fell by 6% yesterday after criticism from patients' advocates, charities and trade unions as well as the Department of Health in London.

Patientline defended the increase, claiming it had to recoup millions of pounds spent on investing in the system. Michael Summers, trustee of the Patients Association, said: "Patients are very concerned already and the proposed increase in percentage terms will mean that, in many, many cases, patients and their families will not be able to afford this.

"It is absolutely beyond the realm of payment for many patients. We are seeing an increasingly ageing population and many of these people will be on fixed incomes. It's too much and too expensive. These companies should not be targeting vulnerable and elderly people."

Last December the company reported interim pre-tax losses of £9.1m, compared to £5.4m the year before. Karen Jennings, head of health for public sector union Unison, said: "To rip off and exploit patients in this way is absolutely diabolical. Being in hospital is often the most distressing and upsetting time in a patient's life.

"Due to money worries about paying for these increasingly extortionate phone bills, many poorer patients will be left even more stranded and out of contact from family and friends.

"We feel Ofcom should investigate this terrible exploitation urgently."

Patientline charges patients £3.50 a day to watch television and £2.20 for one hour on the internet. It says it is reducing the television cost to £2.90 a day to compensate for the higher cost of calls. This will now include free radio, free internet and free games on internet-enabled consoles.

The systems are installed in more than 75,000 UK hospitals. Bedside entertainment and communication systems are in seven Scottish hospitals.

Ofcom, which regulates phone and television services, has previously recommended the Department of Health review hospital bedside telephone and entertainment systems. In January 2006, the regulator said the department should look into "all aspects" of installation and operation of telephone and entertainment systems in hospitals.

It said its investigation found high call prices were a result of a "complex" web of government policy and agreements between providers, the NHS and individual trusts.

A statement from Patientline said: "As Ofcom has recognised, our charges are dictated by the government's contract with Patientline, which means we have to fund and recover all installation (about £1m per hospital) as well as additional day-to-day running costs.

"Patientline has yet to make a profit due to this heavy investment programme and in order to make the reduced costs for TV, internet and games economically viable we had to increase the cost of outgoing calls to 26p per minute from 10p for the time being.

A spokesman for the department of health in Whitehall said: "The cost of incoming calls was not dictated by the Department of Health, as Patientline suggests.

"It is disappointing to learn that Patientline has now increased its charge for patients to make calls from the bedside telephone without formally notifying the department or discussing and agreeing it with trusts in advance.

"The department has sought clarification about a number of issues with Patientline and are awaiting a reply, so that it is able to advise the NHS in the best interest of patients."