LONDON (Reuters) - The world`s 5000 remaining wild tigers are verging on extinction, a British minister said on Wednesday as he launched a United Nations campaign to quash a trade in tiger parts ranging from whiskers to penises. "These animals face a direct threat from poachers who kill them to supply illegal international markets for medicine and skins," environment minister Michael Meacher told a news conference at London Zoo. Meacher was launching a U.N. sponsored mission to halt a five billion dollar a year trade in tiger parts driven by a demand for traditional oriental medicines. The potions use every part of the animal to treat ailments such as asthma and rheumatism. The fact-finding mission by the Convention on International Trade in Endangered Species (CITES) starts in Britain, meeting doctors and retailers of traditional medicines. Other countries to be visited include the United States, Japan, Russia, China, Britain, India and Nepal. Debbie Banks, a campaigner for Environmental Investigation Agency (EIA), said she welcomed the initiative, but hoped political action would soon follow the fact-finding trips. "Without immediate action by the international community the tiger`s future is pretty dim," she told Reuters. EIA surveyed traditional medicine shops in Japan last year and found 17 out of 29 stores illegally selling tiger-based potions, Banks said. This included one shop claiming to sell tiger penises as an aphrodisiac, a use outside the remit of traditional medicine. But trade driven by demand for potions was not the only problem facing the tiger. "The skin trade has certainly not been quashed," Banks said, adding there was evidence one tiger a day was being killed in India, home to most of the world`s surviving wild tigers. Tigers were also dying out because their prey and their habitat was disappearing, CITES spokesman John Sellar told reporters. Asked how long it would be before the campaign would show a positive effect on tiger numbers, Sellar said it was difficult to say, but he hoped to develop "positive strategies" by September.