Raw sewage has been flowing into the River Wharfe for almost three years because of problems at an Otley treatment works, environment officials admitted today.

Yorkshire Water has pledged to step up improvements to the Gallows Hill site after river pollution complaints.

But furious anglers, who spotted human waste and nappies in the river, have accused the Environment Agency of failing to act quickly enough to stop the problem.

Les Magee, of the River Wharfe Anglers' Association, said waste has been leaking from the site since 1999, and he added: "Despite our constant protests, this has gone on ever since. In the year 2002, there shouldn't be thousands of cubic metres of untreated sewage flowing into a river. I cannot believe it has taken so long to get anywhere on this"

The Environment Agency, Yorkshire Water and Leeds City Council held talks with the anglers and Otley MP Harold Best last week in a bid to solve the problem.

And today an Environment Agency spokesman admitted there had been a problem with the treatment works since consent conditions for the site were changed in 1999.

He said: "The circumstances at Gallows Hill have meant the new consent conditions have not worked as effectively as anticipated. It is normal for sewage works to be designed to allow discharges into the river during periods of very high flows, such as storm conditions. However, since the issue of a revised consent, that has happened on an increasing number of occasions.''

A Yorkshire Water spokesman said improvements had been made since the issue was first raised and further work should be completed by June.

"At all times, Yorkshire Water has complied with the levels of consent as set out by the regulator, the Environment Agency," he said.

"We have already made changes which were needed to further improve the works. We are currently awaiting the delivery of the final piece of equipment needed, and this will be in place by the end of June.''

Mr Best said: "I don't think there has been a threat to public health, but it has not been a tolerable situation and that was agreed by everyone concerned.''