The disease, which began in south-east England, has crossed the Scottish border, hundreds of kilometres to the north.

The animals' paws and feet drop off and they die a protracted and painful death. But money to research the outbreak and possible remedies has run out.

Tom Langton, the director of the Froglife Trust, told BBC Radio 4's Today programme: "It's worse than myxomatosis, the plague that devastated rabbit populations.

Painstaking study

"It's a living death: the animals take a considerable time to die, and there are some indications that their numbers are permanently depressed in some areas.

"The ends of their limb extremities, their hands and feet, drop off, they haemorrhage, open sores develop, they get thin and emaciated, and then they die."

Emaciation hastens death

Writing in the magazine, Mr Langton says one theory for the disease's origin is a change in the source of imported goldfish.

Until 20 years ago most goldfish imported to the UK came from Italy, but since then Israel and the US have dominated the trade. In the US, bullfrogs breed alongside the goldfish enclosures, and are often attacked with shotguns to stop them competing for food pellets.

Mr Langton writes: "Bits of bullfrog could be eaten by a goldfish that is netted and flown off for quick distribution to British garden centres.

Instructive life-cycle

"It's a complex situation and the exact causes are still not known. Slug pellets, vehicle emissions and changing weather patterns may play a role in reducing frogs' resistance to the virus; the isolation of urban frogs and in-breeding could also be a factor. More research is needed urgently."

Mr Langton told BBC News Online: "We need �1m for research, but because they're not edible there's no Ministry of Frogs, so we're not getting funding from the government.

Loss of digits is common

"Frogs are also one of the pivotal species in the food chain, converting invertebrates into nourishment for species higher up.

"Every carnivore eats them - herons, badgers, foxes, hedgehogs. And lacking fur or feathers, frogs are ready to go - the hamburgers of the food chain.

Danger periods

"Frogs are hugely important to the British ecology. But we're now bankrupt."

Froglife says the disease was first seen to be increasing in suburban London gardens in the late 1980s.

"Typically, adult frogs are seen to be dying over several weeks, resulting in dozens, or even hundreds, of deaths," it says.

"Reports of the virus reach a peak in July and August. Large-scale frog mortalities also occur in late winter and are usually caused by a garden pond freezing over, which can suffocate male frogs hibernating at the bottom.

"We have found no evidence of the disease affecting people, pets or other pond life; most people report that toads, newts and fish in a pond where frogs are dying appear totally healthy."

Many frogs die protracted deaths

Images courtesy of Froglife/Institute of Zoology