Chimpanzees and monkeys are experimented on but they have brains, so it is like experimenting on the equivalent of a four-year-old child

Actress Lisa Williamson

One speaker told the rally that genetically altered animals were being prepared for the same fate.

"Half a million animals are genetically modified for experiments," said Jan Creamer, president of the National Anti-Vivisection Society.

"By the end of 2002 there will be a million animals, and by the end of the decade these numbers will rise to eight million at current rates of increase."

Wendy Turner-Webster told the protesters that "ignorance and blatant stupidity" lay behind some experiments.

Weedkiller

She highlighted the plight of beagle puppies which were force-fed weedkiller even though the product had been on the market for 20 years.

Lisa Williamson joined demonstrators on their march to Trafalgar Square with a dog called Wookey.

She said: "Chimpanzees and monkeys are experimented on but they have brains, so it is like experimenting on the equivalent of a four-year-old child."

Protesters say many tests are worthless and cruel

Meg Matthews, wife of Oasis star Noel Gallagher, had also been due to speak but was unwell. And Liberal Democrat MP Norman Baker was also missing because his wife has just given birth.

The marchers set off from Hyde Park, where Green Party deputy London mayoral candidate Jenny Jones was speaking, along with Nitan Mehta, of the Young Indian Vegetarians.

The month dedicated to lab animals also includes vigils at animal laboratories.

Campaigners say many lab tests are unnecessary, and do not give reliable information about the effect which the same products or drugs could have when used by humans.