Lie detector tests are being used to identify potential benefit cheats by a council which says the initiative has already saved tax payers £336,711.

Harrow Council, in north west London, is one of a handful of authorities trialling voice risk analysis for the Department for Work and Pensions.

The technology detects changes in people's voice patterns such as hesitation or avoiding direct questions, and identifies them as a "high risk" and in need of further investigation.

There is strong anecdotal evidence that the lie detector test is having a significant deterrent effect on would-be fraudsters.

Over a quarter (281 claimants) were now volunteering information to say that their personal circumstances had changed and they no longer needed benefits - over double the rate at the start of the trial.

Feedback was also said to be 'overwhelmingly positive', with 5% (53 people) refusing to use the technology.