A 15-MILE stretch of the River Irwell has been poisoned after a suspected pollution incident.

Conservation experts say all invertebrates – or ‘river bugs’ – along the waterway from Rossendale to Radcliffe, via Bury, have been 'wiped out', possibly by the dumping of a harmful pesticide.

The vast majority of the bugs have also been wiped out from Radcliffe to Manchester city centre.

An investigation has been launched by the Environment Agency after the incident was reported to the watchdog by the Mersey Basin Rivers Trust, which monitors the Irwell.

Mike Cuddy, the trust’s chief executive, said: “There has been a 15-mile total wipeout of river invertebrates, from a point just south of Rawtenstall to the confluence of the River Roch in Radcliffe.

"There has been a 90 per cent reduction in numbers from Radcliffe down to the city centre of Manchester, where the Irwell joins the Manchester Ship Canal.”

It is feared the pollution could stretch beyond that radius once checks are made of the ship canal and River Mersey.

Sampling teams from the trust, taking part in the national Riverfly Partnership monitoring initiative, first noticed the watercourse had been affected in the Irwell Vale area.

Trust bosses believe the pollutant, which resembles a potent agricultural pesticide called Chlorpyrifos which devastated the River Kennet in Wiltshire and Berkshire four years ago, has been illegally dumped in land drains before reaching the Irwell.

Mr Cuddy said: “We do not think the water company is at fault for this catastrophic incident, rather that an irresponsible individual or business in the sewer network area around the treatment works has illegally disposed of toxic chemicals down the drains.

“This toxin has made its way through the sewer network, through the sewage treatment beds and then into the river via the water treatment works outflow.”