Britain's butterfly population is at a critical all-time low, according to the UK Butterfly Monitoring Scheme.
Persistent summer rains in 2007 prevented the butterflies from mating and feeding, although their population was low even then.
The Lulworth skipper and common blue butterflies are most at risk, with population falls of 73 and 78 per cent respectively.
Butterfly populations have been monitored by The Butterfly Conservation Trust and the Centre for Ecology and Hydrology.
Sir David Attenborough, president of the Butterfly Conservation Trust, said: 'Butterflies face mounting threats. Some face possible extinction.' He has launched the Butterfly Conservation Trust's Stop Extinction Appeal.
Butterfly conservationists say that warm temperatures, little wind, and enough rain to encourage vegetation are essential for butterfly survival.
Dr Tom Brereton, the head of monitoring at the Butterfly Conservation Trust, said: 'Last year butterflies were completely shut down by the weather. We had a brilliant April but then it just collapsed.
'If we have another summer like last year then things will be much worse. Butterflies are quite isolated and if they become absent from an area then it is unlikely that area will be re-colonised.'
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