It is now almost two decades since a surge in public support and visitors saw London Zoo escape the threat of closure.

But as this newspaper's investigation today reveals, the zoo is still grappling with problems. An inspection report last year found animal enclosures to be inadequate and buildings to be dilapidated. This may well be putting the animals at risk, as an incident last year in which 11 penguins were slaughtered by a fox suggests.

Investment is clearly urgently needed. The London Zoological Society's plans to redevelop the big cats' enclosure and the parrot house must, for this reason, be welcomed. Yet this shocking report should also prompt a public debate on whether zoos themselves are, any longer, appropriate.

Our knowledge of animal welfare has grown enormously since the heyday of the great Victorian menageries, when the urban public would gather to see exotic creatures from the far ends of the earth. We now know how much distress is caused to wild animals when they are confined to small cages or paddocks. Even the most well-appointed zoos with the most attentive keepers end up causing distress to animals such as gorillas, tigers and giraffes. A study in 2008 found that elephants in zoos have significantly shorter lives than their wild brethren. And the RSPCA recently called for a ban on all imports of the animals to British zoos on welfare grounds.

The usual defence of zoos is that they encourage children to develop an interest in the natural world and raise money for conservation. But it is a sad day when the only way to instil a respect for wild animals in young people is to subject some of those very animals to a life of artificial confinement and often misery. And, in any case, there is no evidence that the popularity of zoos is correlated with the preservation of natural habitats around the world. It is surely time to let these relics of a more ignorant age fall into permanent disuse. Zoos are giving zoology a bad name.