The organisers of a marriage conference have been told by the Law Society that they can no longer hold the event on their premises.

The Law Society has revoked its permission for the conference, organised by Christian Concern, over concerns that the event breaches its diversity policy.

In an email to Christian Concern, the Law Society’s Adam Tallis said the event was “contrary to our diversity policy, espousing as it does an ethos which is opposed to same-sex marriage”.

Desmond Hudson, chief executive of the Law Society, said: “We are proud of our role in promoting diversity in the solicitors’ profession and felt that the content of this conference sat uncomfortably with our stance. Through our events and venues supplier, we have assisted the organisers in identifying an alternative, non Law Society venue.”

Speakers lined up for the conference included High Court judge Sir Paul Coleridge, who recently launched a campaign to reduce the rate of family breakdown in Britain.

The Bow Group’s Ben Harris-Quinney, ResPublica’s Philip Blond and media commentator Cristina Odone were also due to speak.

The conference had been organised by Christian Concern to debate marriage in light of the Government’s plans to broaden the definition of marriage to include same-sex couples.

The plans have met stiff opposition from church leaders and the wider public, with some Conservative MPs believing that their recent local election losses were in part down to the Prime Minister’s support from gay marriage.

Christian Concern’s Chief Executive Andrea Williams said she was not looking for another venue for the event.

In a statement, she said the Law Society’s decision to close down debate on marriage represented a “fundamental misreading of the Equality Act”.

“Since when can debate be against diversity?” she said.

“This action by the professional body of thousands of solicitors across the UK, all of whom would be supportive of ‘free speech’, demonstrates how discussion on traditional views of marriage is being shut down before any change in the law to redefine marriage has come into force.

“How can the Law Society’s ‘diversity policy’ not include the protection and respect of a range of views on the issue of marriage and, why has the Law Society adopted a pro-same-sex marriage policy ahead of the outcome of the Government’s Consultation and, without consulting its members?

“This colloquium was intended to be a genuine open debate on the issues, constructing a case for marriage in the public sphere, and they seem to be closing it down.”

Mr Harris-Quinney added: “That a broad and professional organisation like the Law Society would decide to attempt to ban such a necessary, salient debate from taking place on their premises is exceptionable, and calls into question the value of their function in representing solicitors in England & Wales in upholding the law of a free nation.”