BBC News Online: UK

'Cannabis' in Parliament Square

The plants are believed to be the result of a May Day "guerilla gardening" campaign by the group Reclaim the Streets.

During the protest a number of seeds were planted and it is thought cannabis could have been among them.

A spokesman for the Royal Parks Police said they had not yet positively identified the cannabis.

"If there is cannabis growing there it will be removed and we will destroy it - it's just a weed," he said.

"Since that May Day thing there have been all sorts of baby plants coming up, seedlings almost."

He added that the plants may not have been sown in the May Day protest.

He added: "Because it's scattered and not in ordinary rows it could have germinated from bird seed."

Police are not expected to prosecute anyone as a result of the discovery.