Matilda Gifford claims police were willing to pay her for information on protest groups

Politicians stepped in when Matilda Gifford revealed that she was approached by officers claiming to be from Strathclyde Police a few weeks after she was arrested in a protest at Aberdeen Airport in March.

Liberal Democrats, Labour and the Scottish Green Party called on ministers to clarify the role of police and ensure their actions were appropriate.

Ms Gifford said she had felt "intimidated" by the experience, which she made public in a series of recordings handed to the Guardian newspaper.

"The main thing about getting this story out was to warn other activists. Other people have been offered money or intimidated like me," she said. "We're not to be intimidated, we must continue to do what we do with a clean conscience. After being scared by these people, I wanted to go public so that I can feel safe."

The 24-year-old said police told her that they have a network of informants inside protest organisations, which they tried to persuade her to join.

In meetings at a Glasgow police station, which she recorded, and later in a cafe, they offered her financial rewards for information on Plane Stupid.

Strathclyde Police Assistant Chief Constable George Hamilton said the force had "a responsibility to gather intelligence".

He added: "Officers from Strathclyde Police have been in contact with a number of protesters who were involved with the Plane Stupid protests, including Aberdeen Airport. The purpose of this contact has been to ensure that any future protest activity is carried out within the law and in a manner which respects the rights of all concerned."

The revelations were described as a "storm in a teacup" by John O'Connor, a former commander of Scotland Yard's Flying Squad, who told the BBC: "The police don't just sit in their ivory tower and expect the phone to ring and be given intelligence information. They go out actively to gather it."