There has been a significant rise once again in the numbers of genetically modified animals used in UK labs.
Home Office statistics for 2002 show GM mice and rats were involved in 710,000 experiments, representing an 11% increase on the previous year.
Rodents are the primary laboratory animal
Altered animals are now deployed in a quarter of all experiments.
The upward trend reflects the greater use made by scientists of new molecular techniques to probe disease.
The effort to understand the fine detail of the human genome is likely to push the numbers of GM animals used higher still in the years to come.
Animals can have genes "knocked out" so that they show symptoms that mimic human illnesses. These "models" of disease can then be studied to find new drug treatments.
Overall, the total number of experiments on animals in UK labs shows an increase of about 110,000, or 4.2%, over 2001.
There were just over 2.73 million regulated procedures in the 12 months from January to January.
Mice, rats and other rodents accounted for 85% of the total, fish and birds for much of the remainder. Dogs, cats, horses and primates combined accounted for less than 1%.
The number of procedures using primates was almost identical to that in 2001.
About 80% of all the experiments are for research and drug development; safety testing accounts for most of rest.
The annual number of procedures in the UK is about half what it was in the 1970s, but experts believe the figures have now probably bottomed out.
They suggest the new classes of drugs now in development that act in very specific ways in the body may actually lead to more animals being used in future years.
New EU proposals on the health and safety aspects of chemicals may also substantially push up the numbers of animals needed for testing.
Home Office Minister Caroline Flint said of the latest statistics: "Research using animals is vital to the development of safe medicines and effective treatment for serious human ailments, and for certain types of research there is currently no suitable alternative.
"It is vital, however, that such tests are only carried out where absolutely essential and done with the minimum of suffering to the animal."
Wendy Higgins, campaigns director at the British Union for the Abolition of Vivisection, said: "This shocking rise, and the alarming increase in the use of genetically modified animals, is a shameful reflection of this government's utter failure to tackle the controversial issue of animal experiments.
"The government is stuck in a policy vacuum on vivisection. Meanwhile the lab animal death toll continues to go up and up."
The BUAV and others - including some in the research community - have criticised the way the statistics are complied.
The figures give little information on the real level of suffering experienced by the animals involved. They also take no account of "wasted" animals - animals bred for their tissues and then discarded or animals rejected because their genetic modifications did not work.
If these were included in the annual statistics, the figures for animal use would be considerably higher.
The Animal Procedures Committee, the government's watchdog in this area, has been asked to come forward with proposals for an improved statistics system.