One pony can be seen curled up in a cramped position evidently trying to make use of the limited bedding. In one of the stables, the bare concrete floor is so dirty and wet it is running with liquid filth.

The squalid conditions belie the bill the charity has submitted to a court for costs in the case. It claims it has spent nearly £250,000 on stabling the ponies since they were seized in February 2017.

The horses are being boarded at a private stable yard in Northumberland while the RSPCA conclude their prosecution of David Hinde, 54, a breeder and Dartmoor pony show judge, who will be sentenced on April 30 in Leeds Crown Court after being convicted earlier this month of breaching a ban on keeping horses imposed in 2011 when he was convicted of causing unnecessary suffering to a pony. He also pleaded guilty to not meeting the needs of 13 other ponies by failing to address the causes of poor body condition.

It is believed around 50 ponies seized in the Hinde case are at the location in Northumberland. Up to 30 are pictured in the leaked photographs, which were taken by a whistle-blower with concerns about their welfare.

In its submission to court, the charity said it had spent £245,126.80 on stabling the horses for two years. In total the charity has submitted costs of £291,633.25  for stabling, transport, vet fees and legal bills.

After being shown the photos, a spokeswoman for the RSPCA said they had sent an inspector unannounced to check on the ponies and were satisfied they were not being neglected.

The spokeswoman said the ponies were only in the stables overnight and that during the day they were turned out in fields. She said they had matted coats because of ‘the change of season’.

The RSPCA spokeswoman said: ‘We appreciate the concerns you’ve raised.  It appears these photos were taken at night when the horses, some of which are on controlled diets, had finished eating their hay and had started eating some of the fresh straw exposing the litter underneath. I’m sure you will appreciate how difficult it is to prevent ponies eating straw bedding; however the straw is of less nutritional content than hay and their eating it does not significantly interfere with their controlled diet.

‘The ponies have fresh bedding every day. Some are kept on deep litter which is topped up with fresh bedding each day.

‘We only leave head collars on, and very occasionally lead ropes, if a pony is difficult to catch, which is sometimes the case with the little or unhandled animals we care for. This pony was due to see the vet so it was important he could be caught quickly without causing him stress.

‘All ponies have fresh water each morning and throughout the day. Hay, straw and other debris can fall into buckets as horses are moving around.’

However, a leading vet and legal experts involved in animal welfare cases claimed none of the above explanations would be accepted by the RSPCA if used as excuses by a defendant they were prosecuting.

Colin Vogel, BVetMed, MRCVS, who served on the Council of the British Equine Veterinary Association, took issue with the RSPCA’s response and said many people had been prosecuted by them for similar conditions.

‘Keeping at least 10 horses in one stables is not in itself wrong, but requires a much bigger stable than photographed. People have been prosecuted for keeping horses in stables that are too small.’

Mr Vogel, who has written numerous respected books about horse care, said the conditions breached best practice as set out by Government.

‘The hay nets are not at the height of the horses heads as required by the DEFRA Code of Practice for welfare of horses. When they are emptied, as here, horses will paw at them and there is a risk of their legs becoming trapped. Owners have frequently been prosecuted on the basis that all the hay nets were found empty – as they are here – on the grounds that horses should have access to forage at  all times. The RSPCA has rejected any argument that it was reasonable for the hay nets to be empty by the morning.’

He voiced serious concern about the lack of water.

‘Horses should have continuous access to water in containers that cannot be knocked over, and owners have often been prosecuted on the basis that on the snapshot of arrival at the premises there was no water

‘Taking the stable of at least 10 homes as an example, they would consume 250 – 500L of water per day spread over the day. If they are stabled for half the 24 hours then you wold expect 125 – 250 L of water to be initially available, but there is no sign of that.’

The horse with a rope attached was at serious risk of injury, he said.

‘The horse stabled with the trailing rope is clearly at risk of injury as a result. What is particularly worrying is that the RSPCA do not appear to accept that there is any risk at all from such a long trailing rope.’

Mr Vogel said that both the scant, dirty beds and lack of hay was similar to cases where people had been prosecuted.

‘On a number of occasions RSPCA witnesses have told a court that deep litter is not an acceptable form of bedding for horses. Where other RSPCA witnesses have accepted that it can be used they have always insisted that sufficient fresh straw must be added every day to ensure that the previous dirt straw is completely covered. That was not done here, where only a small amount of fresh straw can be seen put on top of the soiled straw – a practice which has on a number of occasions be claimed to be unacceptable.

‘Distinction must be made between the stables with soiled straw underneath and a small amount of clean straw and horses that appear to be on a hard floor such as concrete with just a small amount of straw covering just a small proportion of the floor. The latter is never acceptable, and has often been criticised in court.

‘The RSPCA appear to be suggesting that a lack of hay is an acceptable way to limit food intake overnight. Many people have been prosecuted on the basis that their horses did not have access to forage at all times.

‘There does not appear to have been any attempt to use the methods set out in the Code of Practice to reduce calorie intake.  Prosecutions have often claimed that straw is not a suitable feed for horses, but in this case it is apparently suggested that it is. I find it hard to believe that every single one of these horses was on a reduced calorie intake diet. Where such a horse is kept with others it is not acceptable to restrict their feeding as well. They should be stable separately.’

In its own guidelines on horse care on its website, the RSPCA state: ‘Make sure your horse or pony has a healthy diet with constant access to fresh water and as much opportunity to graze as possible. Horses may still need additional hard feed and forage to maintain their appropriate bodyweight.  Things you should do

·         Horses must have continuous access to fresh clean water. ‘

Sara-Lise Howe, a barrister who has defended people being prosecuted by the RSPCA, said: “I have been involved in many cases where the RSPCA have arrived at premises on an early morning raid, and prosecuted animal owners for the types conditions seen in these photos, and better conditions.  From my experience in those cases, the RSPCA rarely – if ever-  accept owner explanations of the type given by the RSPCA in this instance.   Whether or not the RSPCA is correct, it raises worrying issues of double standards.”