Cambridge University's Students' Union said it is "alarmed" by claims that police 'tried to spy' on its members.
The Guardian newspaper has obtained a video of an officer trying to recruit an informant to target protest groups.
The Students' Union said it "condemned" the action and wants the government to look at how UK security forces use surveillance.
The National Union of Students (NUS) described it as "an absolute scandal".
The NUS said it undermines students' right to protest and demands to know just how widespread the practice is.
More top news
In central England and across Scotland, any early cloud will clear, leaving warm sunshine for the rest of the day.
Marks & Spencer has unveiled another year of falling profits as the high street giant counts the cost of its transformation programme.
Philip Roth, one of the great American authors who won the Pulitzer for American Pastoral, has died aged 85.