Like a scene from Alfred Hitchcock's The Birds, large groups of ravens are flocking together to attack defenceless victims and eat them alive.

Throughout the country, farmers have reported a rise in the number of calves, lambs, and sheep pecked to death. Animals not killed have been left in agony as the birds eat their eyes, tongues and the soft flesh of their underbelly.

Farmers are demanding the right to destroy the protected birds, but the Royal Society for the Protection of Birds says it does not see any need for a change to legislation.

The birds - which have acquired mythical status over the centuries, with six being kept at the Tower of London with their wings clipped in case they leave and the kingdom falls - were almost exterminated in many areas during the 19th century. But in the past 20 years they have made a comeback, with colonies as far afield as Inverness, Devon and East Sussex.

'Raven attacks have become a huge problem across a wide area of the country,' said Johnny Hall, head of rural policy for the National Farmers Union of Scotland, which has been hardest hit. 'It's not just an issue with them taking lambs. We have substantial evidence of them attacking adult sheep and calves too. The attacks are so horrific that it's causing mental suffering to people who find the animals.'

Farmers in west Wales also say sheep have fallen prey to the growing raven population. 'The attacks on livestock are becoming a problem, but there's not a lot we can do about it,' said a spokesman for NFU Cymru.