Britain’s rivers, wildlife and plants are being destroyed by what is possibly the worst drought in the south of the UK for 100 years, according to the Environment Agency.

Dead ducks and fish, toxic algal blooms and rivers being reduced to trickles are all becoming a common sight this summer as the drought takes its toll on the environment.

But the problem is not limited to the south, and the EA has issued a map showing more than 100 sites across England and Wales where over the past two months, low water and oxygen levels have caused fish to gasp for air, turned ponds green, and stranded several types of insects that live in water, as rivers dry up.

In other cases, rivers are silting up because of low flows, trees are shedding their leaves earlier than normal, and dry wetlands are causing problems for breeding waders who use the wetlands for food sources.

Dr David King, director of water management at the Environment Agency, said that after two dry winters and the more recent hot, dry summer weather, the environmental impacts of the drought were becoming more apparent.

Dr King said: "This drought is not only affecting people in the way we use water - we've now seen 21 months of below-average rain and the environment is suffering too. We're seeing ponds and rivers drying up, fish becoming stranded and algal blooms."

"At first, we couldn't see the impact of the drought around us, as the real problems were low groundwater levels in the south east. But the continued lack of rainfall, low water levels and recent high temperatures have put pressure on the environment right across England and Wales."

"It’s now clear that the impact of the drought is no longer just contained to the south east of England, where water shortages were impacting on people's water use. The environmental problems are much more widespread."

More than 400 fish of mixed species died in the River Idle in Mattersey, west of Sheffield, and 1000 dead small fish were found in the Counter Drain in Welney, north of Cambridge.

Over 20 fish rescue missions have been undertaken, including about 1000 wild brown trout from the River Nadder, near Salisbury. The fish were moved further downstream.

Low flows in the Thames, which means sea water is flowing further up the river than normal, causing problems for freshwater wildlife. Wetlands, ponds, rivers and lakes drying up, affecting the breeding success of frogs, waders and insects, and some invertebrate species, such as the mayfly, have not been found on chalk streams in the south - their normal breeding ground.

Environmental problems, including dead, dying or distressed fish, should be reported immediately by calling 0800 80 70 60 (free 24 hour service).