Oriental white-backed vultures have seen their numbers collapse (Image: RSPB Images/Guy Shorrock)

Three species on the Asian subcontinent are close to extinction after eating animal carcasses containing traces of the anti-inflammatory diclofenac.

Delhi officials are said to be waiting on final tests of a replacement drug before taking a decision.

A study reported this week showed meloxicam to be a safe alternative.

The three species most seriously affected by diclofenac are the oriental white-backed vulture (Gyps bengalensis), the long-billed vulture (Gyps indicus) and the slender-billed vulture (Gyps tenuirostris).

In the past 10 years, population losses of more than 95% have been reported in these three raptor species.

The link to diclofenac was firmly established in 2004. Tests on captive vultures fed carcass flesh traced with the drug produced symptoms that were strikingly similar to those witnessed in sick birds in the wild.

Diclofenac is a non-steroidal anti-inflammatory drug whose veterinary use on livestock in South Asia has grown rapidly in recent years.

Bird groups told Indian ministry officials at a two-day meeting this week that meloxicam would be a safe and effective alternative. A study published by the Public Library of Science (PLoS) had shown it to be harmless to vultures.

Chris Bowden, who heads the British-based Royal Society for the Protection of Birds' (RSPB) vulture conservation programme, said: "I am convinced that diclofenac will be banned in India this year and possibly within the next six months.

"Without a ban, Asian vultures will become extinct. That would be a tragedy not just for the birds but for the thousands/millions of people for whom vultures are crucial to health, livelihood and religion."

Two Indian ministries are key to the decision to ban diclofenac. Shri Namo Narain Meena, minister of environment and forests, said at the meeting in Delhi: "The most important step to save the vultures, as I understand it, is the complete ban on the veterinary formulation of the drug diclofenac."

But the agriculture ministry, which will make the final decision, has insisted on waiting for the results of last meloxicam tests which are due next week.

Dr Asad Rahmani, director of Bombay Natural History Society, said: "The ministry of environment and forests is fully behind the need for a ban. However our agriculture ministry appears to be the main delay to saving vultures from extinction."

The Indian government has sanctioned a nationwide census of vultures to establish how many remain.

Saving the birds from extinction could have important implications for human health, argue conservationists. As vulture numbers decline, so stray dogs are becoming much more numerous, feeding off the increasing number of unattended animal carcasses.

The danger is that they will spread deadly disease, in particular rabies, which is rife in India.