WHEN the Duke of York opened it two years ago, it was supposed to set a trend in flood relief schemes. But now the Jubilee River, a seven-mile artificial waterway designed to reduce the risk of the Thames bursting its banks, is mired in controversy.

Riverside dwellers downstream from Windsor claim that the £100 million Environment Agency project, the biggest of its kind in England, is not only unsafe but increases the threat of flooding. And they want it closed down.

The watercourse is designed to prevent flooding of communities upstream in Berkshire, where celebrities including Michael Parkinson and Rolf Harris have homes, by taking water from the Thames at Taplow and returning it downstream at Datchet. It was designed to open at times of heavy rainfall, but has been criticised by consulting engineers who uncovered a string of design and construction defects.

Remedial work began in January last year. It has cost £3.5 million so far, with as much again still likely to be spent. January last year was also when the watercourse was last used, during floods in which 500 homes downstream were affected. Water rose to the top of its banks and the channel suffered severe damage, even though the peak flow was only two thirds of its supposed capacity.

Last winter, while Maidenhead, Bray, Windsor and Eton stayed dry, apparently because of the diversion, riverside homes in Wraysbury, Staines and Chertsey found themselves under water.

The finger of suspicion is pointed by residents at the man-made river — otherwise known as the Maidenhead Windsor and Eton Flood Alleviation Scheme. They believe that the flooding of their homes was caused by the extra water that the Jubilee was tipping downstream, raising levels by 18in rather than the few inches promised by the Environment Agency.

And there are bitter allegations that the original decision to save upstream homes from flooding was made at the expense of riverside dwellers downstream.

Jim Wanamaker, 59, a retired geography and science teacher who lives on Ham Island, ten yards from the banks of the Thames, said: “We have always maintained that the housing downstream was sacrificed to save Maidenhead.”

The recently published report by Atkins Consultants, commissioned by the Environment Agency, shows that the banks were built too low, inappropriate materials were used, and that there was a failure to follow standard design criteria.

Windsor and Maidenhead council is furious that, despite the protection afforded by the waterway, the Environment Agency has reclassified areas that it previously described as safe from flooding as being back in the floodplain.

The inauguration of the scheme led to a relaxation of planning regulations and a rush of applications by developers to build houses and extensions in the riverside area.

Vicky Howes, the Liberal Democrat lead cabinet member for planning, said: “The Environment Agency has really cocked this up. They have reverted to the flood maps that were in place before the Jubilee River was built. So in the period after it was constructed planning regulations were relaxed.

“Some housing or extensions are now back in the floodplain and inevitably the issue of property values and insurance (will arise).”

Jubilee River — named after a local competition — can only operate at 81 per cent of the capacity planned by the designers. Atkins has recommended further investigations and survey work, particularly about the height of the river banks and water flow.

The Environment Agency will conduct surveys before further works next summer.

The report identifies a number of problems, including the failure of one of the weirs and the erosion of channel bed protection and embankments.

The natural-looking Jubilee River, which includes 193 hectares of woodland, 250,000 trees and shrubs, wildflower grassland, wetland, nesting cliffs and otter holts, should be closed according to the action-group Community Support Group South.

One campaigner, Ewan Larcombe, a former chairman of Datchet Parish Council, said: “It’s a fiasco turned into a disaster. We were promised that it would not be detrimental to the villages downstream. But the Jubilee River is unfit to use. The gates at the top should be welded shut and it should be filled in again.”

At a cabinet meeting on Thursday councillors expressed dismay that the agency is not offering the protection that the waterway was designed to provide, and demanded an explanation.

Chris Birks, the Environment Agency’s Thames region director, said: “The fact is that in January 2003 a thousand homes in the Maidenhead area that would have flooded otherwise stayed dry.

“We know the Jubilee River works, there is no question about it. Nonetheless, the Atkins reviews do raise important concerns that the Environment Agency is addressing with urgency.”