The leader of one of Britain's most prominent Hindu temples has called for a change in the law after a sick cow was slaughtered on its farm while worshipers were at prayer.

Gauri Das, president of the Bhaktivedanta Manor in Hertfordshire, says reform is needed to ensure the religious convictions of Hindus are respected.

He said the Muslim and Jewish communities had "legal exceptions" allowing specialised slaughter for Halal and Kosher meat.

And he demanded: "Surely as a peaceful community that wants to protect life, we deserve something too?"

Mr Das was speaking after an RSPCA vet killed Gangotri, a 13-year-old Belgian Blue-Jersey Cross, by lethal injection this morning.

It had been unable to stand for more than a year after suffering a muscle injury.

Cows are sacred to Hindus and the killing of one is considered sacrilege.

Mr Das said the farm was assured by the RSPCA and police that no immediate action would be taken, giving them time to mount a legal challenge.

"This is shocking and duplicitous behaviour. We have been deceived by those who had given us their word," he added.

He claimed police bundled away monks attending to the cow in a barn and that the head farmer was kept talking while the injection was administered.

Mr Das said national Hindu organisations would be taking the incident up "at every level" and called for a change in the law so Hindus can allow their animals to die natural deaths.

However, sources said the Animal Health Agency was in contact with the community for some time, advising that the animal was suffering unnecessary pain and that legislation required it be put down.

The owners allegedly refused consent, leading to the events of this morning.

Bhaktivedanta Manor is a stately home donated to the community by late Beatle George Harrison, who was also a student of Hinduism.

Worshippers run The Cow Protection Project which allows old cows and bulls to die naturally.

They accept the cow was sick but say it was receiving round-the-clock care.

But an RSPCA spokesman said it was in "constant pain" and insisted everything had been done to respect religious sensitivities.

"It had been suffering from painful and infected sores, her limbs had become wasted and her breathing difficult," he advised.

"Three separate vets, including from the Royal College of Vets, from Defra and an independent vet have all agreed that the animal was suffering and should be immediately euthanased."

He said the RSPCA, local police and other experts had been in discussion with the community about how to resolve the situation.

"The RSPCA believes animals should not suffer - irrespective of individual religious beliefs."

The incident was raised in the House of Commons by Barry Gardiner, Labour MP for Brent North, who branded it "an outrage" against the worshippers.

Commons Leader Harriet Harman said she understood the "huge strength of feeling and concern" about the incident and pledged to take it up with Environment Secretary Hilary Benn.

The killing of Gangotri follows the controversial slaughter of sacred bullock Shambo in Wales this summer.

Stuart Coyle, head farm manager at Bhaktivedanta Manor, said Gangotri was suffering "tolerable discomfort" and "still going strong".

"Along with with allopathic treatments from our local vet we have also administered a range of alternative treatments which include homeopathy, acupuncture, manipulation, massage and reiki."

He said that despite assurances no hasty action would be taken, police and RSPCA officers arrived suddenly this morning with a warrant.

"During my protestations to the RSPCA officer, another officer came and reported that the cow had already been killed," Mr Coyle added.

"The senior officer had delayed me whilst they sneakily were killing our cow."

A police spokeswoman said: "Officers from Hertfordshire Constabulary were requested to support the RSPCA as they executed a lawful warrant at the Hare Krishna temple."

The Department for Environment, Food and Rural Affairs said: "The Animal Welfare Act makes it an offence to knowingly permit an animal to suffer unnecessarily.

"The Act also allows for an animal, deemed by a veterinary surgeon to be suffering unnecessarily, to be euthanised to prevent further suffering.

"Whilst it is important to respect religious views and seek to accommodate them within the law, it is ultimately necessary to enforce the law if no corrective action to prevent suffering is taken or is possible."

Defra said there were no "legal exceptions" relating to Halal and Kosher meat but directions in Welfare Slaughter Regulations relating to religious slaughter.

By Vivienne Morgan and Joe Sinclair