All the world's a stage – and all the men and women merely environmentalists who hate BP

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 about BP's sponsorship of the World Shakespeare Festival that have divided theatregoers.

The Reclaim Shakespeare Company – a troupe of amateur actor-environmentalists – have appeared at seven productions, condemning in mini-plays BP's environmental record and mocking the RSC's sponsorship deal with the UK oil giant. While the RSC has so far allowed the protests, and many audience reactions have been positive, the latest event saw one staff member try to shout down the activists, while last month members of the group were ejected from the British Museum.

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, a group co-ordinator. "We're concerned about the environmental devastation being wrought by BP, from Deepwater Horizon to their plans to drill in the Arctic. They are not giving sponsorship money to the arts for nothing: their logo is plastered all over these events and it's all about improving their own image."

At the end of each intervention, activists call on audience members to tear the BP logo off their copy of the evening's programme.

BP was widely criticised for safety failures after the Deepwater Horizon oil spill, which devastated coastal communities and wildlife in the Gulf of Mexico in 2010. In Shakespeare-inspired speeches, campaigners also condemn BP's controversial $2.5bn tar sand extraction project in Canada and a recent abortive plan to begin oil exploration in the Arctic.

"We're planning further interventions but I can't say where," Mr Howlett told The Independent. "More and more people are coming on board. We're all theatregoers and lovers of Shakespeare who are concerned about what BP is doing. We hope to make the RSC realise the error of their ways."

The oil giant also sponsors the Tate galleries and was an official partner of the London Olympic Games. The activists claim that their protest has led to a debate within the RSC over whether BP are an appropriate sponsor for nation's chief custodians of Shakespeare's works. It is the RSC's policy to allow the protests to happen "where appropriate and safe to do so".

"BP has sponsored the World Shakespeare Festival as founding presenting partner, and their support has allowed many important elements of the festival to go ahead," said Gregory Doran, the RSC's artistic director. "We consider our potential partners very carefully and the decision to receive sponsorship from BP was taken with the full backing of our Board."

A spokesman for BP said: "Everyone has the right to protest provided they do not disrupt events for the enjoyment of others."