One in five reptiles is threatened with extinction, according to the first comprehensive assessment of more than 10,000 species across the world.

Scientists are calling for urgent conservation action for crocodiles and turtles, which are in a particularly dire situation.

They say reptiles have long been overlooked in conservation, because they are seen as less charismatic than "furry and feathery" creatures.

So far, 31 species have gone extinct.

The study, published in Nature, took more than 15 years to complete, because of problems getting funding for the work.

"Reptiles to many people are not charismatic and there's been a lot more focus on more furry, feathery species of vertebrates for conservation," said Dr Bruce Young of the international nature organisation, NatureServe.

- The venomous king cobra is in decline because of deforestation and human persecution

- Geckos are vanishing in parts of the world due to wildlife trade

- The mugger crocodile: Threatened by habitat destruction and human conflict

- Jamaican iguana: Reptiles on islands face risks from invasive species and sea level rise

Despite their low publicity profile, the cold-blooded vertebrates play an essential role in the balance of life.

"Reptiles are good for people because they help control pests such as insects and rodents," said Prof Blair Hedges of Temple University in Philadelphia, US.