The decision by the Metropolitan Police to discontinue the investigation into a serial cat killer after concluding it was foxes has been criticised.

The Metropolitan Police announced the findings today after reports that a serial cat killer, known as the Croydon Cat Killer, was behind the slaughter and mutilation of up to 500 pets across the UK, including Wickford, Billericay and most recently Leigh.

For three years, police and animal activists have been trying to trace a culprit, also dubbed the M25 cat killer, who was suspected of bludgeoning animals to death before dissecting their corpses.

At one point a team of 15 Scotland Yard officers was deployed on the trail of the suspect.

But today Scotland Yard announced a review of all the evidence had found no trace of human involvement, with no CCTV sightings, no witnesses and no forensic leads.

The force revealed that a vet who had carried out post-mortem examinations of six “suspicious cat deaths” had “re-assessed” his findings of human involvement - despite initially concluding they had been dissected with a sharp instrument.

Animal charity SNARL (South Norwood Animal Rescue and Liberation) have been heavily involved in the investigation and have attended hundreds of scenes where suspected victims had been found.

The charity has said they were left stunned by the announcement by the Met.

Co-founder Boudica Rising said: "We are aware of the notification this morning by the Met Police that they are discontinuing Operation Takahe, due to new evidence that suggests the injuries to the cats are fox predation post- road traffic accident or other event.

"As you can imagine, this morning’s announcement has come as a surprise and we will be taking advice on how to move forward.

"We consider that the evidence we have gathered over the last three years does indicate human involvement and there is expert opinion to back this up.

"Over the last three years, we have discounted over 1500 incidents as non-human related.

"The police have said that they will continue to investigate incidents where there is clear evidence of human involvement.

"Our priority at the moment is the victim’s families and we will release a further statement in due course."

The news has also frustrated those who were suspected victims of the killer.

Kayley West, 33, of Leigh, was heartbroken to find her cat had been killed earlier this month.

Hearing the news, she said: "As much as we would love to believe this was foxes, facts show otherwise.

"My family and I have owned cats all our lives and this has never happened before and I do not personally know anyone else this has happened to.

"Clearly the police are at a dead end and it is easier to blame foxes. Let’s just hope this sick individual never moves on to humans."

However, national animal charity the RSPCA, who have also been involved in the investigation, has said it is pleased with the outcome.

A spokesman for the charity said: "An RSPCA spokesman said: “The RSPCA has supported the Metropolitan Police in its investigation into a number of cat deaths over the past three years and we’re pleased that the inquiries have come to a conclusion.”