Muslim leaders have demanded the same legal exemptions as the Church of England in legislation to introduce gay marriages.
The Muslim Council of Britain (MCB), with more than 500 affiliated mosques, charities and schools, said it was "appalled" by "utterly discriminatory" legislation on gay marriage set out by the Government.
The proposals would allow faith groups to conduct gay marriages but would ban the Church of England and the Church in Wales from doing so.
MCB secretary-general Farooq Murad said his organisation had strongly opposed gay marriage alongside other religions and was seeking an urgent meeting with Culture Secretary Maria Miller to express the concerns of the Muslim community over the proposals.
"No-one in their right mind should accept such a discriminatory law," he said. "It should be amended to give exactly the same exemption to all the religions."
The criticism from the MCB comes after the Church of England last week attacked the Government's lack of consultation over its gay marriage plans, saying senior ecclesiastical figures learned of them only when Mrs Miller announced them to Parliament.
But the Department for Culture, Media and Sport said it would have been "inappropriate" to discuss the fine print of its plans before telling Parliament. Mrs Miller told the House of Commons that she was putting in place a "quadruple lock" of measures to guarantee religious organisations would not have to marry same-sex couples against their wishes.
Under the plans, four legal "locks" will be included on the face of the legislation. No religious organisation or individual minister could be compelled to marry same-sex couples or to permit this to happen on their premises. It would be unlawful for religious organisations or their ministers to marry same-sex couples unless their organisation's governing body has expressly opted in to provisions for doing so.
The Equality Act 2010 would be amended to ensure no discrimination claim can be brought against religious organisations or individual ministers for refusing to marry a same-sex couple.
The legislation will also explicitly state that it will be illegal for the Church of England and the Church in Wales to marry same-sex couples, she said. As the established Church, Church of England vicars must marry any eligible couples regardless of their faith. Under Canon Law, the laws of the Church of England, marriage is defined as between a man and a woman. Any change to this to introduce same sex unions would have to be approved by the General Synod of the Church of England.