RSPCA inspectors called to an underground lair were shocked to find a dog hanging dead by its lead.

An adult male brown and white springer spaniel was found by a passer-by in a brick-built bunker in woodland, close to Spring Bank Rise in Keighley.

He had been hanged by the neck from a rope lead attached to a choke chain. The lead had been knotted to a bar inside the bunker.

Horrified RSPCA inspectors, who went to investigate, said the dog, which was also suffering a severe skin complaint, would have endured a "slow and painful" death and had been hanging there for about two days.

They were called on Tuesday after a passer-by discovered the body.

It was taken to a vet where a post mortem examination was carried out. The vet confirmed the dog died 48 hours earlier as a result of strangulation.

RSPCA inspector Dave Holgate, who attended the scene, said: "This was a shocking act of cruelty.

"This dog would have undoubtedly endured a slow, painful death and suffered horribly in its final moments. It was a deliberate act - the dogs back legs were touching the ground and it had been supporting itself at the time, so it would not have been a quick death. It would have taken hours to die."

Inspector Holgate warned whoever had carried out the act of cruelty towards the dog could face huge fines of even jail.

Under the Animal Welfare Act 2006, causing unnecessary suffering to a protected animal carries a maximum sentence of six months in prison, a £20,000 fine or both.

Inspector Holgate said: "The dog was not wearing a collar and had a microchip that was not registered so it is impossible to trace an owner at this stage. We're now hoping someone may be able to provide information to help us find who he may have belonged to.

"I urge anyone who saw, heard or knows anything about this disturbing incident to contact us urgently. It is such a ghastly thing.

"I have never come across anything like this in 15 years as an inspector and I hope I never come across anything like this again."

Anyone with information should contact the RSPCA on 0300 1234999.

e-mail: marc.meneaud