... And the beast that nobody loves

There is no sympathy for the despised cockroach, not even in an animal sanctuary. As pest control officers seek to exterminate them in houses and restaurants across Britain, even the insect lovers who visit London Zoo regard them with loathing.

Hilda the hissing roach is the least favourite of the 12,000 animals in the zoo. Even the West African assassin bug - who stabs other insects to death with its tongue and injects them with poisonous saliva - has more admirers.

Others win lifelong friends. John Cleese, the actor and comedian, was so taken with the zoo's black-and-white ruffed lemur that he adopted him under the zoo's Lifewatch scheme. The television presenter Jonathan Ross has adopted a bat, the actress Lynda Bellingham has taken on a shark, the entertainer Rolf Harris has - inevitably - a kookaburra, and Leslie Grantham, formerly Dirty Den from BBC1's EastEnders, chose a flamingo. But no one will touch the hissing roach.

The British obsession with pet-keeping is generating nearly pounds 1m a year for zoos through animal sponsorship in which businesses and individuals are asked to pay an annual fee to cover the board and lodging of an animal. There are now 46 British zoos running schemes and Chester Zoo's alone makes pounds 100,000 a year.

The most popular animal for adoption is the Sumatran tiger. The most expensive is the Asian elephant at London Zoo, which will set you back pounds 6,000 a year. If you want an elephant, but the price is too high, you could adopt a share - say half a tail - for pounds 30.

Last month, London Electricity paid pounds 6,000 to adopt an elephant called Dilberta. Dorothy Griffiths, the company's community affairs manager, said the adoption idea tied in with its programme for teaching schoolchildren the importance of energy conservation.

"Our mascot for that programme is an elephant called Ellie. It is based on the old adage that elephants never forget," she said. "For our money we get a small plaque in the Elephant House and we have access to Dilberta on special occasions for photographs."

Adopters may also get a certificate and an information pack on the animal they have chosen. Other packages include free entrance tickets, photographs, badges and posters of your animal. But for some this is not enough; they regard themselves almost as foster parents.

Marie Le Fevre, a regular visitor to Paignton Zoo in Devon, adopted some monkeys and became so devoted to them that she left pounds 250,000 in her will to build a new monkey house.

Another patron of a West Country zoo was enraged when she discovered that a member of a colony of marmosets which she had adopted had died from old age a week earlier without her knowledge.

At Edinburgh Zoo you can adopt a film celebrity - one of the penguins registered with Equity for performances in television advertisements for chocolate biscuits. And penguins are also popular at Drusillas Zoo Park in East Sussex, where Nuglas, a local window replacement company, won the corporate race to sponsorship of the birds' enclosure. Kitty Ann, the zoo's owner who introduced animal adoption to Britain in the mid-Seventies, said adopters could choose their own price for the animals they took into their care.

"It is a bit unfair to say one animal is worth more than another," Ms Ann said. "We don't want to hurt anybody's feelings." The Wildfowl and Wetland Trust is also cashing in on adoption schemes. At the Martin Mere centre, near Ormskirk in Lancashire, fowl fans have been queuing up to join the pounds 10 "Love-a-Duck, a truly wild idea!" scheme, now renamed more conservatively as the Adopt-a-Duck project.

At Martin Mere there are also opportunities to Guard-a-Goose for pounds 17, or Nurture-a-Nene, a rare Hawaiian bird, for pounds 20.

Not everyone is enthusiastic about animal adoption, however. Some animal rights groups say that the schemes are simply a means for prolonging the precarious existence of zoos and claim that companies which invest in the projects are misreading the public mood on captive animals.

Les Ward, director of Animal Advocates, an Edinburgh-based animal protection pressure group, said: "If a company believes this is good public relations then I would say they are onto a loser.

"People are becoming more and more aware that animals require more to enrich their lives than a cage where they pace up and down all day while people laugh and point at them.

"These companies are being given bad advice. If they want to help they should send their money to the countries where these animals come from so it can be spent on nature parks and anti-poaching patrols."

8 Adopt an Animal, London Zoo, Regent's Park, London NW1 4RY; 0171 449 6262

London Zoo's top 10 adoptions

1. Sumatran tiger

2. Black-footed penguin

3. Asian elephant

4. Asian lion

5. Gorilla

6. Senegal bushbaby

7. Chimpanzee

8. Giraffe

9. Black rhinoceros

10. Grey wolf

The 10 least

popular adoptions

1. Hissing cockroach

2. Assassin bug

3. Viper

4. Hermit crab

5. Rat

6. Pony

7. Flamingo

8. Frog

9. Millipede

10. Chameleon