The board of the Cochrane Collaboration, a prestigious group that reviews health evidence, has been reduced from 13 to 6 members, following a controversial vote to expel a member for the first time in its 25-year existence.

On 14 September, Peter Gøtzsche, director of the Cochrane’s Nordic centre and a member of its governing board, posted a statement on the centre’s website announcing that he had been expelled as a member of the Cochrane Collaboration, after a vote by 6 of 13 of the board’s members.

A further four elected members of the board — which also has appointed members — later stepped down in protest. To maintain a balance between appointed and elected members required by its statutes, the board also asked two appointed members to resign.

Gøtzsche says that no justification was given for the expulsion but that he was accused by the board of bringing the organization into “disrepute”. The organization — which carries out systematic reviews of health-care interventions — told Nature it had received “numerous complaints” about Gøtzsche after the publication earlier this year of a critique he co-authored, entitled ‘The Cochrane HPV vaccine review was incomplete and ignored important evidence of bias’ and published in the BMJ Evidence-Based Medicine.

The ructions come as the collaboration — which has 11,000 members in 130 countries — meets for its general assembly in Edinburgh, UK. According to two board members contacted by Nature, collaboration members at the meeting are expected to vote to dissolve the current board entirely over the issue.

A statement by the board’s remaining members on the Cochrane’s website, posted on 15 September, says that at its meeting it had, as planned, “considered the findings of an independent review and complaints related to the conduct of a member”. It said that the board’s “conclusion was communicated to the individual concerned and is part of an ongoing process. The Co-Chairs of the Board will provide further details once this process is complete”.

Gøtzsche’s statement says that there is a “growing top-down authoritarian culture and an increasingly commercial business model” taking root at Cochrane that “threaten the scientific, moral and social objectives of the organization”. He has also been an outspoken critic of Cochrane’s relationship with the pharmaceutical industry. (Cochrane’s policies state that its reviews cannot be “funded or conducted by commercial sponsors or commercial sources with a real or potential vested interest in the findings of a specific review”.)

David Hammerstein Mintz, a board member who stepped down in protest, said some members thought that Gøtzsche’s critical views of Cochrane were “disloyal”. (Nature has approached the collaboration for comment on these points and is awaiting its response.) “It might have been a headache, but the harm done by expelling Peter is much greater than any inconvenience caused by scientific debate,” he says.