They are now urging a systematic review of all existing animal research before new experiments are carried out.

The findings, published in the British Medical Journal, have boosted animal rights groups.

However, on the same day that the BMJ paper is published, the Royal Society has produced a guide which says humanity has benefited immensely from scientific research involving animals.

The society, which is the UK's national academy of science, says virtually every medical achievement in the past century has been reliant on the use of animals in some way.

In contrast, the London School of Hygiene scientists question the point of some animal experiments, citing examples where research has been badly designed or where it has been carried out alongside human trials, rendering it unnecessary.

In reaching their conclusions, the London team carried out a systematic review of all animal experiments which purported to have clinical relevance to humans.

They found many weaknesses and believe animal testing needs to be reviewed.

POTENTIAL EXPERIMENT FLAWS Species so different from man that findings may not be applicable Drug doses may be very different from those given to humans Small experimental groups generating weak conclusions Variability in the criteria for selecting animals The way illness or injury is induced may vary too much from the human condition

"We are only asking that the same standards as are applied in human research are applied to animal research, said Professor Ian Roberts, one of the authors of the report. "We would not tolerate haphazard potentially biased reviews of human research so why should we tolerate this for animal research?

"New research, whether in animals or humans, should only be carried out after a proper systematic review of the existing research.

"What's more, comparing results from systematic reviews of animal and human research will allow us to assess the contribution of animal research to improving human health." Testing benefits

The team stress they are neither in favour of or opposed to animal experiments.

Professor Colin Blakemore, chief executive of the Medical Research Council (MRC), backed the Royal Society's stance.

He said: "Animal research has contributed to virtually every area of medicine.

There is evidence some research is badly designed . "Antibiotics, vaccines, heart surgery and kidney transplants have all been discovered and tested through animal studies.

"However, it's imperative that animal research is properly evaluated before the results are transferred to medical practice.

"The sample size of this BMJ study is small, but the authors have identified some ineffective clinical treatments that were based on inadequate analysis of results from animal research."

He stressed that animal studies have indicated when it is not appropriate to move to human trials as much as when it is.

The MRC's policy is that animals must only be used where it is strictly necessary and we are committed to developing alternatives to animal research.

He pointed out that the vast majority of the animal research work funded by the MRC is not for trials of new drugs but for studies of disease processes and how the body works.

"Where we do fund clinical trials of potential new treatments, we expect animal studies to be completed before human studies begin," he said.

"Furthermore, researchers are expected to demonstrate what potential positive or negative effects have been found in animals."

Animal rights groups say the BMJ paper is a major breakthrough in the scientific community's willingness to debate the issue of animal experiments and whether they work.

National Anti-vivisection Society chief executive Jan Creamer said: "Currently, we only see the results of animal experiments years after they have occurred - when the researcher publishes the work.

"This can be between three and 10 years after the event. So the debate about whether animals should have been used takes place too late.

"We want to shift this to the position where there is full public scrutiny before a licence is granted."

This news reported by BBC was posted on the website of Animal News Centre - www.anc.org