A species of mussel which could devastate Britain's wetlands and cost thousands of pounds in water bills has been discovered in a reservoir near London Heathrow Airport.

Quagga mussels were found in Britain for the first time in the Wraysbury Reservoir last week, the Wildfowl and Wetland Trust (WWT) has revealed.

The molluscs, originally from the Ukraine, measure less than 5cm long but breed so prolifically their vast colonies, which attach on to hard surfaces, can smother boat hulls, block pipes and potentially cause flooding.

Wildlife experts have described them as ecosystem engineers due to their vast capacity to filter water which upsets the natural balance of the food web as they eat pollutants then turn them into concentrated toxic faeces which can poison drinking water for both wildlife and people.

Earlier this year the quagga mussel was unanimously identified by scientists as the greatest single threat to Britain's wildlife of any alien species.

Jeff Knott, WWT's head of conservation policy, said: "This is a worrying, but entirely predictable, development that could be devastating to British wetlands. Quagga mussels are likely to indirectly cause suffering and death for hundreds of thousands of native animals, fish and plants and cost millions of pounds in tax and water bills to protect drinking water supplies.

"These tiny mussels can be devastating but look so innocuous, which is why it's so difficult for boaters, anglers and other water users to avoid accidentally transferring them between water bodies when they latch on to their equipment. That's why it's so important for all water users to remember the motto 'clean, check, dry' when they pack up their equipment to help slow the spread."

He said the devastating effect of the mussels is why the UK needs stronger controls on invasive species being brought into the country as prevention is far cheaper and more effective than trying to control an established infestation.

"We need to protect the UK against the next invasive species", he added.

The spread of quagga mussels is often due to human activity as adults, who can produce one million eggs a season, attach themselves to boats.

Engineers at the Hoover Dam in America's Lake Mead are battling the invasion of the mussels as they colonise the dam's turbines and block pipes supplying water to Las Vegas after they were introduced by ships discharging ballast in the Great Lakes.

Anyone who finds a suspected quagga mussel should report it via www.nonnativespecies.org/alerts/quaggamussel

A Defra spokesman said: "It is important that we take action to address the threats posed by invasive non-native species. They threaten the survival our own plants and animals and cost the economy at least £1.8 billion a year

"We will be working closely with interested parties and our agencies to reduce the risk of the quagga mussel spreading any further. Users of our waterways can help with this by checking their equipment and keeping it clean and dry."