A petition opposing the Government's plans to change the definition of marriage has reached 600,000 signatures.

The petition by the Coalition for Marriage (C4M) was launched in February and has grown to become the biggest active campaign in the UK.

It calls upon the Government to retain the current definition of marriage as a union between one man and one woman.

The Government plans to expand the definition of marriage to include same-sex unions despite strong opposition.

A ComRes poll suggested 70% of the population was against redefining marriage.

Colin Hart, Campaign Director of C4M, said: “I hope that the Government will start listening to the millions of people who support the current definition of marriage and who are at a complete loss as to why the Government has brought forward these proposals.

“Over 600,000 people have told the Government: we value marriage and do not want to change its meaning. The Government would be advised to listen to its voters.”

The petition has continued to attract support despite "cheap insults being thrown at our supporters by the Deputy Prime Minister", Mr Hart continued.

Nick Clegg found himself at the centre of a row this week after calling opponents of gay marriage "bigots". The remark was made in a draft speech written and distributed to the media by his press office. The speech was later recalled and amended to replace the word "bigot" with "some people".

The Government has also come under fire for refusing to publish legal advice on the implications of legalising gay marriage.

Leaked emails sent by officials from the Scottish Government to their counterparts in London appeared to give weight to the concerns of legal experts and Christian organisations.

There are fears that clergy will be forced to conduct gay wedding ceremonies despite assurances from the Government.

One unnamed official said in a leaked email that the Government would have to change legislation, including the Equality Act 2010, in order to ensure "full protection" for individual celebrants who refuse to conduct same-sex ceremonies.

“Why is the Government continuing to refuse to publish legal advice confirming the concerns of MPs, legal and constitutional experts, the Scottish Executive and even one of its most senior members Eric Pickles?” Mr Hart said.

Mr Pickles told the Telegraph newspaper that there had to be protection for churches and other places of worship to protect them from being forced to carry out same sex wedding ceremonies.

Mr Hart continued, “We have consistently warned that introducing gay marriage will have serious implications. Experts warn it will affect those conducting marriage ceremonies, teachers and parents, the school curriculum and on those who work in the public sector.

“The Government must spell out the full range of legal implications that making this change will have. Legal and constitutional experts are increasingly alarmed by the Government’s undemocratic and trivialising approach to rewriting the definition of this ancient institution.

“If the Equalities Minister really believes that this change will have no effect on those individuals and groups who do not support their proposals, then they should publish the legal advice."