Burglars have broken into a world-famous garden designed to warn against the misuse of drugs and stolen its collection of cannabis plants.

Thieves have stolen seven plants and propagating equipment from Alnwick Gardens, the only poison garden in the UK.

The controversial garden was opened by the Duchess of Alnwick in February. Although branded by anti-drug campaigners as "irresponsible", supporters said it was a valuable tool in teaching children about the dangers of drugs.

However, on Friday night intruders entered one of the greenhouses and made off with its stock of cannabis plants.

Following the embarrassing theft, the trust which runs the gardens has had all the remaining cannabis plants destroyed. It has now instigated a review of security although a spokesman said it hoped to reinstate the display of cannabis plants at the popular tourist attraction next year.

The Duchess of Northumberland said yesterday: "The Alnwick Garden Trust is committed to drugs education and the theft of the cannabis plants from the Poison Garden serves only to underline the importance of this work.

"The charity will continue to educate thousands of children each year on the dangers of drugs and poisonous plants.

"The Poison Garden's appeal of danger stimulates debate; after all young people are more fascinated by which plants can kill you than which plants can cure you."

The garden, which has attracted more than 120,000 people since it opened, is home to more than 50 rare, toxic and dangerous plants, including cannabis, opium poppies, magic mushrooms and coca, the source of cocaine, along with species such as tobacco and deadly nightshade.

It was granted a Home Office license to cultivate the drugs after promising there would be tight security surrounding the most dangerous plants.

Crispian Strachan, the former Chief Constable of Northumbria Police who attended the opening of the £400,000 poison garden said: "Knowledge and education and awareness must come first.

"After that we can talk about the illegality and dangers. The Poison Garden is a valuable educational tool and a source of infinite curiosity for many people."

A spokesman for Northumbria Police said: "We can confirm that we are investigating a burglary at the Alnwick Gardens, which happened between 5pm on Friday, September 30 and 7am on Saturday, October 1.

"Several panes of a greenhouse were smashed and seven cannabis plants were taken from inside along with related growing equipment. "We would appeal for anyone with information about the burglary to contact police in Alnwick."

Anyone with any information about the theft is asked to ring (01661) 872555.