By Adrian Addison
BBC Six O'Clock News reporter
The Royal Society for the Protection of Birds (RSPB) fears pet fairs could introduce bird flu into Britain and spread it across the country.
Species are available from across the world
Europe is racing to bolster its defences against bird flu, fearing migrating wildfowl could introduce the disease to the continent.
But the RSPB believes the trade in caught wild birds could pose a greater risk than natural migration patterns.
It is urging the government to ban the trade in pet birds.
Whilst authorities stress the risk is low, Dutch farmers have been ordered to keep poultry locked up inside, British doctors have been briefed on a nightmare scenario of a human pandemic and France is stockpiling drugs to protect its population.
But a special investigation for the BBC Six O'clock News has uncovered what experts fear is a far greater risk - the trade in birds at dozens of pet fairs across Britain every weekend.
Bird fanciers meet in scout huts and school halls across the UK to buy and sell pet birds.
Neil Forbes, one of the UK's leading bird vets, told the BBC: "These places are a cauldron of infection.
"How can you honestly have a hall filled with birds, some of whom have potentially fatal infections to humans, where the public are allowed to walk in. It's madness.
"And how are they cleaned? Haven't we learnt any of the bio-hazard lessons from foot-and-mouth?
"It's horrific to think that the next day you might have a Women's Institute meeting or a creche or whatever and have old people breathing in this dust.
"Or children crawling around the floor, up close to the floor and chairs - breathing in potentially infected particles."
The H5N1 strain of bird (or avian) flu, which surfaced in Hong Kong eight years ago, has killed more than 50 people in Asia, led to the destruction of millions of birds, and has now started to spread west.
Birds can be bought cheaply at fairs
"The nightmare scenario is you could import a bird from the Far East that carries this virus, that brings it into an auction hall and spreads it to a number of others," Mr Forbes added.
"That then distributes it across the UK and we then end up slaughtering every chicken in the UK.
"And, potentially, humans becoming ill - and some of them dying of the disease."
At present the virus is not thought to be able to jump from human to human.
But what scares experts most is the possibility that it could mutate and develop this ability - possibly sparking a pandemic to rival the killer global flu outbreaks of the last century.
Julian Hughes, the RSPB's Head of Species Conservation, told the Six O'clock News: "The RSPB thinks that the risk of avian influenza being brought into the country through bird trade and through these bird fairs is far greater than from migratory water fowl coming in or from migration from Siberia.
"So we think that the government has to act, and act quickly at a European level to ban the trade in wild birds."
The Parrot Society is Britain's number one club for bird lovers. They argue these events should continue.
Parrot Society Chairman Cliff Wright said: "If it's done correctly it can be policed.
"If it's stopped, it'll finish up in motorway services, in a local car park or in the back street, the back room of a pub. They'll still be sold, but they'll be sold undercover.
"There are still youngsters coming up today who'd like a hands on approach.
"It's all well and good saying leave stuff in the wild but there'll be no wild to leave the stuff in the way things are going in this world. What do you do, look at pictures?"
Greg Glendell is a bird behaviourist and director of the Birds First organisation.
He told the BBC: "These events are disgusting. It's basically just a car boot sale for birds.
"If this was happening with cats and dogs, if I was driving a white van around from one fair to another like this auctioning cats and dogs off, someone would stop me.
"But because it's birds, it doesn't matter. You wouldn't sell cats and dogs like this; the police would come down on you and the RSPCA would come down on you."
The law governing bird fairs is a mess. Some, such as the Animal Protection Agency, argue that they are already, essentially, illegal - but the law is rarely enforced.
And the government is currently drafting a new Animal Welfare Bill which could put an end to these events. Many think it should.