Police have defended a "barbaric" decision to buy GPS locating devices to trace people with dementia who disappear.

Sussex police have bought six battery-powered locators as part of a attempt to save money and time spent on searching for dementia patients.

The National Pensioners Convention described the introduction of the devices as "barbaric" and suggested people could be stigmatised and made to feel like criminals.

But Sergeant Suzie Mitchell said: "The scheme is only costing Sussex police a few hundred pounds but, comparing this to police time, resources, potential risk to the missing person, let alone the anxiety and worry for their family, it is, in my opinion, a few hundred pounds well spent."

The Mindme GPS device is monitored by Chichester Careline, run by Chichester district council, and supports vulnerable people 24 hours a day. It can be attached to house keys or kept round a person's neck and enables those who become lost or disorientated to be found by their families through a website or the careline.

As long as wearers have a mobile signal, they can be located anywhere in the world, officials said. Information on their whereabouts is given only to the carer or family after security checks.

The device is seen as a way of helping police who say they are regularly called out to help find people with dementia .

But Dot Gibson, the pensioners convention general secretary, said: "I think they should withdraw it straight away. Trying to equate somebody who has committed a criminal act with somebody who is suffering dementia is completely wrong. I doubt whether anyone in the cabinet would want their parents dealt with in this way if they were suffering from dementia."

Gibson accused the authorities of "trying to get care on the cheap", adding: "It looks at the problem in the wrong way. If you've got people in the community who are so bad that they are wandering off at night and are not safe, they should be properly cared for; they shouldn't be tagged.

"It's a crude form of monitoring when the issue needs a much more detailed response than this. This is a back-of-an-envelope response."

There are believed to be more than 800,000 people with dementia in the UK. A number of local authorities are already using similar devices, but this is believed to be the first time a police force has taken on such a scheme.

The devices cost £27.50 a month, which includes Chichester Careline monitoring it round the clock, every day.

Eileen Lintill of Chichester district council said: "Hundreds of thousands of people across the country have dementia. This solution gives both those with dementia and their families the confidence and reassurance they need.

"The latest model also allows customers to speak to us directly by pressing a button. This can be used by anyone who wants to maintain their independence, but have the reassurance that someone is always around to help them."