Drunken parties are causing havoc on Oxfordshire's waterways, Environment Agency bosses have warned.

There have been numerous incidents on the river Thames since the start of the year and EA managers fear it is only a matter of time before there is a serious accident or a tragedy.

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

Agency bosses say drunken party revellers frequently fall into the river at locks and they are urging boaters to limit their drinking.

Chris Mullineux, waterways operations team leader for the EA in the Upper Thames region, said: "Large single-sex groups tend to be on a binge when they are boating on the river and we often see them go hell-for-leather from the hire base to get to the nearest pub as quickly as they can.

"There could be a serious accident or even a tragedy arising from drunken handling of these boats and we strongly advise against it.

"Falling into the water near a propellor which is turning fast could inflict very nasty injuries."

Mr Mullineux said the Thames Conservancy Act 1932 gave the EA the power to deal with "dangerous navigation" but it was difficult to enforce.

He added: "The legislation needs tightening up, and the Department for Transport is considering introducing a breath test for all waterways.

"There is no harm in having a glass of wine or two when you are out on the river but some of these dos are drinking much more, and the women can be just as bad as the men."

Boat hire company Anglowelsh at Eynsham is one of the firms which has suffered from drunken parties.

Steve Allcock, general manager, said: "Last month, a stag party went out, got rowdy and broke the TV aerial on a narrowboat.

"Another boat on the river claimed the stag party hit them but they denied it afterwards and we have banned them from hiring out boats again.

"We give the parties all the tuition they need and tell them that the person steering the boat has to stay sober."

Not all parties act irresponsibly though. Nicky Palfrey, 39, and 20 friends from Somerset and Gloucester set off from Eynsham to Lechlade from Anglowelsh in Eynsham on Friday in two 60ft narrow- boats.

She said: "This started out as a birthday celebration nine years ago and we have been doing it ever since. We drink one or two glasses along the way and we stop overnight in pubs but we don't overdo it. We make a long weekend of it.

"Before we set off, staff at the boat hire company remind us that someone has got to stay sober and we don't do anything stupid. No-one has ever fallen in."

Warwick Smith of the Department for Transport said: "There is no law against drinking alcohol and steering a private craft, but it is against the law to do it with a commercial craft.

"This is an issue that the Government is looking at but at present there are no firm proposals for changes."

There have been 20 significant near-misses in the Upper Thames region so far this year, many alcohol-related and the majority involving stag dos.

Earlier this year, two boats collided at Kings Lock near Godstow Last month, a boat crashed into the lock gate at Osney Lock and a man risked his life by tightrope-walking along the guardrail of the weir Last year at Pinkhill near Farmoor, two stag do parties raced their hire boats until one crashed into another boat on a bend One out of 10 single-sex parties on the river causes the Environment Agency problems