To BP, or not to BP, that is the question environmentalists are asking of the RSC

The protesters' character, 'BP', greets theatregoers as they make their way out

It is a Saturday night in Stratford-upon-Avon and theatregoers are settling into their seats for an evening with the world's greatest playwright.

Duly the actors appear on stage – but this isn't Shakespeare as we know it. Parading in a green and yellow ruff, a character called BP is taken down a peg by the Bard's famous clown, Feste: "for some are born green, some achieve greenness, and some purchase a semblance of greenness by sponsoring cultural events."

The performance, an unscheduled prelude to last weekend's Royal Shakespeare Company (RSC) production of Twelfth Night, was the latest in a string of protests that have attacked BP's sponsorship of the World Shakespeare Festival.

Calling themselves the Reclaim Shakespeare Company, a band of amateur actor-environmentalists have appeared at seven productions throughout the year, staging mini-plays condemning BP's environmental record and mocking the RSC for signing a sponsorship deal with the UK oil giant.

While the RSC has so far allowed the protests to go ahead and many audience reactions have been positive, the latest protest saw one staff member try to shout down the activists, while last month members of the group were ejected from the British Museum by security staff.

The group has vowed to target more events in the festival calendar. "BP are using our cultural institutions as a means of improving their public image at a time when it is crucial for people to see what a dangerous company this is" said Richard Howlett, 30, an acting graduate from Oxford who helps to coordinate the group.

A spokesman for BP said the company had been "a proud supporter of the arts in the UK for over 30 years, helping to bring arts and culture to millions of people". "Everyone has the right to protest provided they do not disrupt events for the enjoyment of others," he added.

Gregory Doran, the RSC's Artistic Director, said: "We consider our potential partners very carefully and the decision to receive sponsorship from BP was taken with the full backing of our Board."