Turkey must respect the human rights treaty it signed up to and give gay and lesbian citizens their rights to peaceful assembly and freedom of association, a leading EU politician has said.

Michael Cashman, an MEP for the West Midlands, was speaking in the wake of the decision of a court in Istanbul to close Lambda Legal.

A department of the Istanbul Governor’s office responsible for non-governmental organisations alleged that the group, Lambda Istanbul, violates Turkish laws on morality.

Last week a court in Islanbul agreed that Lambda breaches both the Penal Code, as an association in violation of “law and morals,” and Article 41 of the Turkish constitution, which is concerned with “the peace and welfare of the family.”

The court ordered Lambda Istanbul to close. It was founded in 1993 and registered as an association in May 2006.

“This is an extremely worrying development”, said Michael Cashman, who is President of the European Parliament’s Intergroup on Gay and Lesbian Rights.

“This is a regressive step in terms of Turkey’s accession to the European Union.”

Mr Cashman is one of only two out MEPs.

Earlier this year he took part in an LGBT rights march in the Turkish capital Ankara alongside members of Lambda.

His Intergroup colleague Sophie In’t Veld, a Dutch MEP, said:

“It is a clear violation of Article 11 of the European Convention on Human Rights.”

“Freedom of association is a human right of every person. You can not take this right away just because a person is homosexual, bisexual or transgender.”

Lissy Gröner, Vice-President of the Intergroup, said:

“If Turkey is to enter the EU, it should not forget that human rights are a part of acquis communautaire.

“We, the politicians in the European Parliament, will now pay a special attention to the respect of human rights of LGBT people in Turkey.”

The President of the Parliamentary Assembly of the Council of Europe has also issued a stark reminder to the Turkish government that freedom of expression and freedom of association are enshrined in the European Convention on Human Rights, which Turkey has ratified.

Lluis Maria de Puig expressed his “profound concern” after the banning of Lambda .

“The arguments put forward by the prosecutor, reportedly leading to the closure of the association Lambda Istanbul, whose activities were held to infringe the laws on public morality, are puzzling to me,” said Mr de Puig, who is a Spanish Socialist.

Turkey is an official candidate for EU membership, but there are deep divisions and misgivings about allowing the mostly Muslim nation to join.

The UK is a vocal supporter of Turkish membership.

Concerns about human rights have delayed and frustrated negotiations.