The wettest May to July on record during 2007 prevented the insects from warming up enough to become active, fly and reach their food sources.

Cool and damp conditions last August compounded the previous year’s low breeding rates.

The bad weather affected many species that had already suffered from increases in intensive agriculture, habitat loss and poor conservation management, according to Tom Brereton, head of monitoring for the group Butterfly Conservation.

He says one of the most threatened species is the high brown fritillary, which now has fewer than 50 colonies across the UK, many of them very small.

Other threatened butterflies include the pearl-bordered fritillary and the wood white, which has less than 100 colonies.

“If we have a nice sunny year with only bouts of rain some species will bounce back, but some species got to such a low ebb on some sites we're not sure if it has tipped them over the edge of extinction,” Brereton told reporters.

Butterfly Conservation recommends that Britons expand their gardens to provide oases for the insects. Planting colorful flowers and native species of grass can also help the butterflies as well as the caterpillars from which they come.

Photo: Jeremy Early - Nature Conservation Imaging