Violence broke out at Glastonbury Festival on Friday night after members of direct action group Art Uncut clashed with security staff over U2's tax status.

Security guards were quick to stamp out a planned demonstration to release a 20-foot balloon emblazoned with the message "U PAY TAX 2?"

Members of the UK Uncut offshoot complained that security guards had used "heavy-handed" tactics to suppress the peaceful protest.

Art Uncut has since issued a statement on its blog:

"If they can get away with it, the wealthy establishment tend to hire heavies to crush dissent...We wanted a dialogue with U2, on an issue that is crucial for international development. Instead we got heavy-handed security tactics; our highly visible expression of conscience was pulled down after just a few minutes - where are the festival's radical roots now, we ask?"

The Irish rock band has been criticized for its "convoluted" tax affairs after moving its commercial operations to the Netherlands in 2006, where royalties on music incur virtually no tax.

Art Uncut says that U2's decision to move its operating company (U2 Ltd) to the Netherlands is depriving Ireland of tax revenues at a time when money is desperately needed.

The group maintains that their action was crucial to "get people thinking about the ethics of taxation, and the relationship between tax and development".

Art Uncut also held a separate "Bono pay up!" protest in Kentish Town over the weekend including talks by John Christensen, director of Tax Justice Network, and Maurice Glasman, a leading proponent of the 'Blue Labour' movement.