Police chiefs were urged yesterday to review their use of paid informants after a climate change campaigner revealed how she was offered money for information about protesters.
Scottish police were asked to explain why they had made contact with members of the protest group Plane Stupid and to clarify the extent to which financial incentives had been offered in exchange for information.
Matilda Gifford, 24, a member of a group arrested at a demonstration at Aberdeen airport in March, recorded conversations with two men said to be members of Strathclyde Police. A possible financial deal was discussed that could have helped Ms Gifford with her student loan fees. "You wouldn't pay any tax on it. So you could do with it what you want," she was told.
Police use of paid informants is not uncommon. But there were calls for the Scottish Parliament to investigate the allegations, with critics urging that police make a distinction between informants able to provide insider knowledge of criminal gangs and those linked to campaigning organisations.
Shami Chakrabarti, director of Liberty, the human rights group, said: "People hearing this story will be rightly alarmed and sceptical of the proportionality and legality of this tactic. They will wonder whether these sources are being recruited to report on trouble at protests or stir it up."
Liberal Democrat home affairs spokesman Chris Huhne said: "There has to be a clear respect for legitimate and peaceful protest. The police must not be seen to be undermining the democratic right to demonstrate."
Strathclyde Police's Assistant Chief Constable, George Hamilton, said: "The purpose of this contact has been to ensure that any future protest activity is carried out within the law."