Boaters who drink too much booze on Oxfordshire waterways could face jail, the Government has said.

Ministers confirmed a new alcohol limit will be introduced for leisure boaters - including people in charge of punts and narrowboats - to bring them in line with professional sailors and motorists.

The proposed legal limit, 80 milligrams of alcohol per 100 millilitres of blood, means two pints of normal strength beer or a large glass of wine could put someone over the limit.

The announcement follows warnings from the Environment Agency that drunken stag party revellers are risking their lives by falling into the Thames at locks.

The new offence, of being "involved in the navigation of a vessel" while over the limit, will be punishable by a fine of up to £5,000 or two years' imprisonment. It is expected to come into force as early as next year.

A spokesman for the Department for Transport confirmed that punters and narrowboat drivers would be expected to take a breath test if asked to do so by police.

Bob Dowling, of the Cherwell Boathouse, off Bardwell Road, North Oxford, said: "As a responsible firm we would have to work within the law.

"At the moment our practice is that anyone who is drunk does not go out in a boat."

There have been nearly two dozen near-misses in the Upper Thames region so far this year.

Emergency services said many were alcohol-related and the majority involved stag parties.

In May, a stag party hired a narrowboat and crashed into the lock gates at Osney Lock, while earlier in the year two boats collided near Kings Lock, Godstow.