A horse abandoned in a field without food, water or shelter became so ill that it had to be put down.

The animal collapsed in a field near Stevenage’s Monkswood Way on Thursday morning.

Animal lovers tried to help it before an RSPCA inspector and a vet arrived but a decision was made to put the horse down after the animal’s condition continued to deteriorate.

One woman bystander said: “It was unbelievable. I was so upset with what I saw. How can the people who own these horses treat them like this? It’s absolutely disgusting.”

It is thought the animal may have become ill after eating a toxic tree or plant, something the woman puts down to the lack of grass in the field.

“It’s completely bare of any sort of nourishment for these animals,” she said.

“There have been up to four horses in that field with nothing to eat so they end up eating trees and anything they can find which might make them ill.

“I go down there every day and give them something but it’s not enough. There’s no shelter for them at night either, and it can get very cold. I think it’s disgraceful that this has been going on for so long and nothing has been done.”

The animal was dumped along with a pony and is part of a group of horses that have been sporadically ‘fly-grazing’ on the field for the past few months.

By law the horses cannot be legally transported away until they have been reported as abandoned for a minimum of two weeks.

The owners of these horses have been regularly removing them before this deadline, only to put them back again a short time later when the legal clock restarts.

Fly-grazing is a growing problem in England and Wales and MPs are currently discussing how to close this loophole.

Herts police confirmed it is aware of the dumped animals but as it not a crime there are not investigating.

A spokesman for the RSPCA said anyone who knows who owns the horses should call its inspectorate line on 0300 123 8018.