There are more than 85 unofficial Sharia courts operating in the UK, a new report by the rightwing think tank Civitas has revealed.
The courts, which usually apply Sharia law in family or financial disputes, can have their rulings upheld by civil courts in England and Wales under the 1996 Arbitration Act.
Decisions from the tribunals can be presented to a family court judge on a two page form for approval.
The new report from Civitas, calls for a new law to stop Sharia rulings from being legally enforceable.
Denis MacEoin, a former lecturer in Arabic and Islamic studies who wrote the report said: "The fact that so many Sharia rulings in Britain relate to cases concerning divorce and custody of children is of particular concern, as women are not equal in Sharia law, and Sharia contains no specific commitment to the best interests of the child that is fundamental to family law in the UK.
Mr MacEoin opines that the "courts are advising illegal actions" and are incompatible with human rights law.
The Muslim Arbitration Tribunal (MAT), a network of Sharia courts, has been operating in London, Manchester, Bradford, Birmingham and Nuneaton since 2007 under the 1996 Arbitration Act. These make decisions that are legally binding and can be enforced by the English courts, provided they do not conflict with English law and both parties choose to use them.
An MAT spokeswoman said that critics of any use of Islamic law failed to recognise that both parties had to agree to any form of dispute resolution in Britain.
"The establishment of Muslim Arbitration Tribunals is an important and significant step towards providing the Muslim community with a real opportunity to self determine disputes in accordance with Islamic sacred law," a statement from the organisation said.