An experiment in which mice died after being given amphetamines and exposed to loud dance music has been criticised by the Home Office.

Cambridge University scientists involved in the study have received an official reprimand, it was revealed on Monday.

However, anti-vivisection campaigners have described this as a "slap on the wrist", saying that the team should have been prosecuted for animal cruelty.

The experiments, led by Dr Jenny Morton, involved 238 mice, some of whom were given the drugs and then exposed to music from the dance group The Prodigy at high volume.

Seven died, and some others were left brain damaged. Some others who were exposed to the classical composer Bach instead also died.

Mice injected with salt water rather than drugs fell asleep instead.

Brain effects

The study was designed to study the effects of amphetamine on a part of the brain called the striatum, suggesting that "environmental stimulus" might enhance the toxicity of the drug.

However, animal rights groups were outraged, describing the research as "tasteless and horrific".

Infringement

On Monday, a year after the results of the study were first revealed in the journal NeuroReport, the Home Office said it had taken "infringement action" against the team.

This amounted to "formal admonitions" and a reminder about the rules under which animal research should be carried out - which state that animals should not be exposed to "unnecessary suffering".

Why should they get special treatment just because they are scientists?

Wendy Higgins, British Union for the Abolition of Vivisection

A spokeswoman for the Home Office said: "The music and drugs study was a by-product of Huntingdon's Disease research.

"It developed into a separate piece of work which went beyond the procedures authorised by the original project licence."

Wendy Higgins, from the British Union for the Abolition of Vivisection, said: "It's disgusting, they should be prosecuted for animal cruelty.

"Why should they get special treatment just because they are scientists?

"The whole relationship between the Home Office and researchers is far too cosy.

"Mice have just as much ability to suffer as dogs, cats or guinea pigs. The scientists deliberately brain-damaged and killed these animals, and all they got was a ticking off."