The World Society for the Protection of Animals and the Born Free Foundation urged stricter controls, higher professionalism and a fund to finance the care of animals after a zoo closes down.
But yesterday Joe Gipps, director of London Zoo, said the report, The Zoo Inquiry, was biased and shallow. 'No respectable zoo would claim it's making all of the running on wildlife conservation - we're just doing our bit.'
The report was a response to last year's World Zoo Conservation Strategy, which London Zoo helped prepare. It showed that only about 1,200 zoos out of roughly 10,000 world-wide were registered for captive breeding and wildlife conservation.
The Zoo Inquiry says only 2 per cent of the world's 5,926 threatened or endangered species of higher animals are registered in zoo breeding programmes. Only 16 projects have successfully returned animals to the wild.
Will Travers, of the Born Free Foundation, said: 'There may be as many as five million animals confined in the world's zoos. Most are there for little more than human entertainment.'
The Government has published laws to implement the European Union's Habitats Directive, intended to protect wildlife.