Rob Evans, The Guardian

Police carried out surveillance on political campaigners while they were at the Glastonbury Festival, newly released documents show.

Details of their activities were recorded in a clandestine database run by the secretive police operation which has infiltrated a network of spies into political groups for 40 years.

Police logged how the campaigners had set up a stall at the festival and were selling what police termed "political publications and merchandise of an XLW anti-capitalist nature". The letters XLW are understood to mean "extreme left-wing".

They were mainly selling T-shirts and badges, along with DVDs and books. The police officers also recorded the home address and mobile phone number of the campaigner who had booked the stall.

The campaigners had been in the Green Fields, a special area – described as "the soul" of the festival – which hosts stalls and speakers on political ideas.

Disclosure of the documents comes as police have faced criticism over the intrusiveness and scale of their surveillance operations against political campaigners following revelations about the activities of nine undercover officers.

Simon Wellings, one of the undercover officers who has been unmasked, infiltrated the anti-capitalist group which was spied on at Glastonbury.

Evidence of the surveillance has been obtained by Guy Taylor, a 45-year-old activist working for the group, Globalise Resistance, following a request under the data protection act.

He obtained his file from the database which shows that police identified his presence at 27 demonstrations for causes such as anti-racism, opposition to the Iraq War and climate change between 2006 and 2011. One entry records how "Globalise Resistance had a campaigns stall at the Glastonbury Festival" in 2009 and that "this stall was selling political publications and merchandise of a XLW anti-capitalist nature".

Police had established that it was Taylor who gained approval from the festival organisers to set up the stall.

Taylor said: "I can't understand what use information about what I did at Glastonbury has for the Metropolitan police.

"If they need to know the plans and schemes of anti-capitalists, the worst place to look is Glastonbury as we were rarely in a fit state to plan the downfall of a parish council let alone the world financial system as we know it."

The Green Fields, described by Glastonbury organisers as encapsulating the "spirits and ideals" of the original festival, is home each year to an eclectic mix of activities including environmental initiatives, tipis, massages and solar-powered marquees. Taylor, has a conviction dating from 1991 for spray-painting anti-war slogans, is one of thousands of campaigners whose political activities have been recorded covertly on the database since 1999 and shared with police forces across the country.

The database, currently run by the Metropolitan police, contains information from undercover officers, informants in protest groups, covert intercepts and reports of demonstrations from uniformed officers.

Another activist on the database is John Catt, an 87-year-old campaigner with no criminal record. Police recorded how he attended more than 55 demonstrations over a four-year period, detailing how he brought along his sketchpad and made drawings of protests.

The Metropolitan police said it was not prepared to "discuss individual cases nor the provenance of information held on police databases".

A spokesman added: "The Management of Police Information (MOPI) statutory code of practice provides a clear framework for the collation and retention of information for policing purposes. The National Domestic Extremism Unit (NDEU) database is maintained according to this code of practice.

"The retention and collation of intelligence reports – carried out in accordance with the appropriate statutory codes of practice – is vital enabling us to fulfil our obligations of protecting life and property, preserving order, preventing the commission of offences, and bringing offenders to justice".

He said this "important principle" was upheld when the high court recently dismissed an application by Catt to have his file deleted from the database.

Last year, Newsnight reported that Wellings's real role was revealed following a blunder. He inadvertently phoned a campaigner from the Global Resistance group on his mobile phone while analysing photographs of protesters with a police officer at a police station. © Guardian News and Media 2012

Photo from Unofficial Glastonbury Festival via Flickr