The agency says the River Eden needs action

The agency says more needs to be done to protect them from waste from farms and sewage treatment works.

Figures show that in England and Wales, almost 20% of rivers designated as sites of special scientific interest (SSSI) - the UK's top conservation status - have poor water quality.

The agency says the River Eden in Cumbria and its tributaries, one of the best catchments in the North West for otters, has been singled out for action against pollution from agriculture.

In North Yorkshire the River Derwent, a protected SSSI river, is also suffering.

The River Derwent is home to rare wildlife

It is home to a number of valuable species, including one of only two surviving remnants of the primitive invertebrate, the agnatha or "jawless fish".

Investigations by the Environment Agency have highlighted the need to reduce the levels of phosphates entering the river from sewage treatment operations.

High phosphate levels were found in 54% of all rivers in England and Wales.

In 2002 the Environment Agency surveyed 7,000 sites, along 25,000 miles of rivers and canals, for their chemical and biological water quality.

The Agency said tighter enforcement of discharge consents, along with cooperation from industry on pollution prevention and control, had reduced the number of so-called pollution hot-spots.

But it said there are still too many pollution incidents.

In 2002 there was a total of 1,468 serious pollution incidents, 21% less than in 2001, but still more than in 2000.