The government has defended an increase in the use of animals in scientific testing.

Last year, 2.73 million scientific procedures were performed using animals, an increase of 4.2 per cent since 2001.

Of those, nearly two thirds were for fundamental biological research, while nearly a fifth were for toxicological testing.

Rodents were used in 84 per cent of cases, compared to 12 per cent involving fish or birds and less than one per cent using dogs, cats and horses.

"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," said Home Office minister Caroline Flint.

"It is vital, however, that such tests are only carried out where absolutely essential and done with the minimum of suffering to the animal."

She added that the UK "has the toughest legislation in the world on the use of animals in scientific procedures".

But the Liberal Democrats accused the government of breaking pledges.

"The rise in animal experiments flies in the face of the government's 1997 commitment to reduce testing on living animals," said environment spokesman Norman Baker.

"Too little attention has been paid to funding alternatives to experiments, requiring data sharing and eliminating unauthorised experiments."