Drunken yobs will be forced to stay sober and made to wear so-called ‘sobriety tags’ in a scheme unveiled by Boris Johnson in Croydon this morning.

Under the terms of the pilot, up to 150 offenders at a time will be fitted with the tags and ordered to not drink alcohol or be sent to prison.

The first order was passed at Croydon Magistrates’ Court earlier today, where the scheme was launched.

The tags wil be given to people in Croydon, Sutton, Lambeth and Southwark.

If anyone who is tagged has a drink it is detected by the tag and they could be brought back in front of the judge to face further punishment, which could include a prison sentence.

The Mayor of London said: "There’s no particular reason for choosing Croydon for the launch but it is a particular coincidence that here today the first alcohol abuse management requirement has been issued by the court against somebody.

"That’s good news because it will allow us to test a new way of tackling alcohol related crime.

"The group that we are particularly targeting is people that drink a bit too much and get in a fight and rather than incarcerate them, give them a chance to get off the drink."

Having had a drink last night the Mayor added: "I would not have wanted to be wearing one last night but these tags aren’t targeted at me.

"They are targeted at people involved in violence and that type of offence.

"I’m told by judges that they are very effective."

Croydon and Sutton London Assembly member Steve O’Connell kicked off the trial by wearing a tag for 48 hours and had it taken off at the launch.

He joked that he had a drink last night because "The last thing you want is for it to come up with zero for the trial."

The tag works by recording alcohol emissions - measuring air and sweat emitted from the skin every 30 minutes.

The pilot is the delivery of an election manifesto pledge by the Mayor to lobby for new sentencing powers to tackle alcohol related crime through a compulsory sobriety scheme.

It is based on a programme in South Dakota, USA, set up by former White House drugs adviser Professor Keith Humphreys.

This saw 99 per cent of tagged offenders’ tests coming back negative and the jail population falling by 14 per cent.