Human and feathered protesters have presented a petition of 33,000 names to Downing Street, calling for a ban on the importation of wild birds.
Polly gone: campaigners say extinction threatens the birds
Around 100 protesters, and 12 parrots on board a London bus, joined a march starting from Trafalgar Square.
Campaigners say taking parrots from their natural habitat is destroying rainforests and that many of the animals die in transit.
They want all EU countries to ban the importation of the birds.
The US has already implemented such a ban.
World Parrot Trust director Jamie Gilardi said the Labour Party had made a statement in support of a ban in 1997 and called on Tony Blair to follow up on that.
The European Parliament has supported a ban in the past but one has not made it through the European Commission.
Mr Gilardi said: "We had far more signatures on the petition than we expected. The response has been phenomenal.
"Parrots are very smart. We want this stopped as they are now becoming extinct."
The trust, based in Hayle, Cornwall, is working with the RSPCA and the Parrot Society UK to campaign for a ban.
'WHO'S A PRETTY BOY, THEN?'
There are 358 species of parrot, including cockatoos, lovebirds and budgerigars
Australia and the Amazon are home to the most species
Many parrots are gregarious and live in large flocks
Egyptian hieroglyphics feature pet birds including parrots
Ancient Greeks kept parrots in cages of precious metal
Illustrator and children's author Quentin Blake was among the protesters, having become interested in the cause after being asked to illustrate a World Parrot Trust T-shirt.
"There has to be an EU reaction to this. Wild parrots are one of the most astonishing aspects of the world and their habitats should not be destroyed," he said.
A Department for Environment, Food and Rural Affairs (Defra) spokesman said there were "robust conditions in place" on the importation of wild animals to ensure protection of species.
But he added: "We are always happy to listen to the case and hear any evidence being put forward by conservation groups."