Three out of four rivers in England and Wales have failed tough ecological tests introduced by the European Union.

Only five of the 6,114 rivers and their tributaries have reached the highest ranking for the overall quality of their eco-systems. Of these, four are in Northumberland — the Ridlees Burn, Barrow Burn Catchment, River Till and Linhope Burn — and the fifth is the river Caletwr in North Wales.

A total of 117, some 2 per cent of all rivers, were found to be the dirtiest and most inhospitable to marine, plant and invertebrate life. Among them is the Stour estuary in Kent, part of a nature reserve run by the RSPB.

But even famous chalkstream rivers such as the Test, a favourite stretch for anglers, is in trouble. Paul Knight, of the Salmon and Trout Association , said: “People may not think of the Test as failing because it is cleaner. But the new system of scoring rivers means that when you look at the ecology — the number of fish, plants, invertebrates and the tiniest bugs — it is not doing well. The main problems are linked to over-abstraction and lack of river flow and diffuse pollution from phosphorus from laundry detergents and nitrogen from pesticide run off from farmland.”

Only a quarter of rivers are judged as in high or good status.

Nevertheless, the Environment Agency says that rivers are cleaner than they have been for 20 years even if more work is required. Species such as salmon, otter and eels have returned to the Thames, the Tyne and the Mersey.

The agency’s tests on chemical content of rivers show quality to have improved overall for 19 successive years.This has been thanks to investment by water companies, action against polluters, and greener farming practices.

Paul Leinster, chief executive at the agency, said: “We need to go even further to meet the new EU measures for water quality. That is why we have announced plans to clean up 9,000 miles of river over the next five years. Our strategy will tackle the pollution and obstructions that prevent wildlife returning to some areas and we will working with farmers, water companies and groups such as the RSPB.”

Ministers have already decided to ban the use of phosphorus in washing powders and liquids. The precise moves and a timetable are still to be drawn up but a ban will also apply to phosphorus in industrial cleaning products.

Plans to improve each river basin are being submitted by the agency to Hilary Benn, the Environment Secretary, who must agree future work by the end of the year.

Conservationists, however, are unclear how experts intend to achieve the higher standards.

Experts from wildlife and angling organisations have formed the “Our Rivers” campaign to press for urgency to protect the waterways.

Mark Avery, director of conservation at the RSPB, said: “These alarming figures show just how far we have got to tackle the problems. There are just five rivers in pristine condition left and they are all in some of the least densely populated corners of the country.

“Elsewhere we are having a devastating impact on our waterways, Pollution from agriculture, over-abstraction and poor town planning are all threatening an extremely important habitat for wildlife, Otters, water voles, kingfishers and more than 30 species of fish rely on our rivers.”

Times recommends

• Energy-saving ideas from switched-on professor
• Rooks are as clever with tools as chimpanzees
• Burping of the lambs blows roast off menu