Butterflies in the UK are facing “a vital” period following a worrying decline in their numbers, naturalist Sir David Attenborough has warned.

The TV broadcaster said some of the UK’s most common species have suffered “significant declines” in recent years.

Many have experienced “several poor years”, he added, due to cold weather and with their habitats under threat.

Warm weather this year has given some species, such as the meadow brown and red admiral “a good start”, he said.

More than three quarters of the UK’s butterflies have declined in the last 40 years, with numbers falling quicker in towns and cities, experts say.

Sir David, president of Butterfly Conservation, said that despite a warm summer last year, species like the small tortoiseshell, peacock, meadow brown and gatekeeper had seen numbers fall due to a warm winter and a subsequent cold spring.