Britain has among the toughest legislation on animal experiments in the world. The Animals (Scientific Procedures) Act of 1986 controls any experimental or scientific procedure applied to an animal which may have the effect of causing it pain, suffering, distress or lasting harm. Both the scientist and the research project need separate licences, and any subsequent changes to the project must be registered and approved before the work can continue. It is therefore dismaying that the pressure group Animal Aid should feel it necessary to call for a boycott of medical charities that support animal experiments.

First, it re-opens a debate that most scientists considered closed: why we need to experiment on animals. Animal experiments have played a critical role in just about every medical breakthrough of the last century. They are vital for testing the safety of drugs and vaccines, from common painkillers to advanced anti-cancer treatment. They may not be perfect, and human trials are also vital, but without them medical advances would be seriously hampered. Cancer, strokes, heart disease, diabetes, Parkinson's and Alz-heimer's are just some of conditions for which animal experiments have benefited research.

There are alternatives. Drugs can be tested on human tissue and living cells grown in the laboratory. But it will be years before they replace animals. What alarms many is the sharp rise in animal testing over a decade – which reflects the big increase in funding for medical research, public and private. The development of genetically modified animals has also improved understanding of how humans will respond to a treatment.

So we are learning more from animal experiments than in the past. Genetically modified animals accounted for over half of all animal experiments in 2009, compared with just 8 per cent in 1995. More than nine out of 10 of these animals were mice and rats. Animals have been used by man for thousands of years – for food, clothing and as beasts of burden. Medical testing, provided it is done humanely and kept to a minimum, is another benefit we should welcome, while continuing to develop alternatives.