Letter was written in support of artist Rachel Ara who is crowdfunding a legal case against Oxford Brookes University, after it cancelled lectures she was going to give

Leading gay rights charity Stonewall has been accused of censoring debate on gender identity and suppressing academic freedom.

More than 20 professors, researchers and lecturers have signed a letter criticising the charity for providing UK universities with a template on transgender issues.

According to the letter, this template does not allow dissenting views or criticism from academics who think differently.

The academics also claim that questioning Stonewall's policies opens them up to harassment from students.

The charity's policies go far beyond equality law, critics say.

The letter, sent to the Times, was co-ordinated by Kathleen Stock, a professor of philosophy at Sussex University.

Signatories include Simon Fanshawe, former chairman of Sussex University council and one of the founders of LGB Alliance.

LGB Alliance broke away from Stonewall over its approach to transgender issues in October.

The letter was written in support of artist Rachel Ara, who is crowdfunding a legal case against Oxford Brookes University, after it cancelled tutorials and lectures she was going to give at the last minute last month.

Ms Ara, who says she draws a distinction between biological sex and gender identity, claimed that the university's LGBTQ+ society wrote to its vice-chancellor complaining about her invitation.

Critics claim Stonewall transgender policies do not allow dissenting views or criticism from academics who think differently

The letter was co-ordinated by Kathleen Stock (left), a professor of philosophy at Sussex University. Signatories include Simon Fanshawe (right), former chairman of Sussex University council and one of the founders of LGB Alliance

Ms Ara claims that the Oxford Brookes University (pictured) LGBTQ+ society wrote to its vice-chancellor complaining about her invitation, leading to her lectures being cancelled

After her appearance was cancelled, the university said that correct procedures had not been followed.

In a letter to the university, Ms Ara's lawyer, Paul Conrathe, links the cancellation to Stonewall.

He said that Oxford Brookes is one of several universities who follow the charity's policy.

Mr Conrathe argues that this means the university's policies and training are drawn up 'on terms dictated by Stonewall', which 'treats any dissenting views as transphobic'.

Ms Ara is demanding that her invitation to speak be reinstated within three months.

She is also calling on the university to amend its policies that she believes restrict academic freedom.

The legal action could set a precedent for other universities that have also been accused of harming academic freedom in similar situations.

Paul Twocock, the chief executive of Stonewall said: 'We're proud to work with over 750 organisations, including universities, as part of our diversity champions programme to help make their workplaces more inclusive for lesbian, gay, bi and trans people.'