Five sharia courts have been set up in London, Birmingham, Bradford and Manchester and Nuneaton, Warwickshire. The government has quietly sanctioned that their rulings are enforceable with the full power of the judicial system, through the county courts or High Court. Previously, the rulings were not binding and depended on voluntary compliance among Muslims.
Lawyers have issued grave warnings about the dangers of a dual legal system and the disclosure drew criticism from Opposition leaders.
Dominic Grieve, the shadow home secretary, said: "If it is true that these tribunals are passing binding decisions in the areas of family and criminal law, I would like to know which courts are enforcing them because I would consider such action unlawful. British law is absolute and must remain so."
Douglas Murray, the director of the Centre for Social Cohesion, added: "I think it's appalling. I don't think arbitration that is done by sharia should ever be endorsed or enforced by the British state."
Muslim tribunal courts started passing sharia judgments in August 2007. They have dealt with more than 100 cases that range from Muslim divorce and inheritance to nuisance neighbours.
It has also emerged that tribunal courts have settled six cases of domestic violence between married couples, working in tandem with the police investigations.
Sheikh Faiz-ul-Aqtab Siddiqi, whose Muslim Arbitration Tribunal runs the courts, said that sharia courts are classified as arbitration tribunals under a clause in the Arbitration Act 1996.
The rulings of arbitration tribunals are binding in law, provided that both parties in the dispute agree to give it the power to rule on their case.
The disclosures come after Rowan Williams, the Archbishop of Canterbury, sparked a national debate and calls for his resignation for saying that the establishment of sharia in the future "seems unavoidable" in Britain.
In July, Lord Phillips of Worth Matravers, the Lord Chief Justice agreed that Muslims in Britain should be able to live according to Islamic law to decide financial and marital disputes.
Mr Siddiqi said he expected the courts to handle a greater number of "smaller" criminal cases in coming years as more Muslim clients approach them. Two more courts are being planned for Glasgow and Edinburgh.
"All we are doing is regulating community affairs in these cases," said Mr Siddiqi, chairman of the governing council of the tribunal.
There are concerns for women suffering under the Islamic laws, which favours men.
Mr Siddiqi said that in a recent inheritance dispute handled by the court in Nuneaton, the estate of a Midlands man was divided between three daughters and two sons.
The judges on the panel gave the sons twice as much as the daughters, in accordance with sharia. Had the family gone to a normal British court, the daughters would have got equal amounts.
In the six cases of domestic violence, Mr Siddiqi said the judges ordered the husbands to take anger management classes and mentoring from community elders. There was no further punishment.
In each case, the women subsequently withdrew the complaints they had lodged with the police and the police stopped their investigations.
Mr Siddiqi said that in the domestic violence cases, the advantage was that marriages were saved and couples given a second chance.
