Nick Herbert, the Minister for Policing and Criminal Justice, has become the latest member of the government to join the Out4Marriage campaign to support efforts to legalise gay marriages.

Joining the Home Secretary Theresa May and Deputy Prime Minister Nick Clegg in recording a message for the campaign, Mr Herbert said the difference between civil partnerships and marriages matters.

Mr Herbert speaks of being the first Tory to “be open about their sexuality when elected” and “incredibly grateful” to have been able to have a civil partnership.

Speaking of his own civil partnership, Herbert says it was “the most important thing that’s happened in my life and it was because of the courage of members of parliament who saw how important it was to make that happen.”

However, Herbert adds: “But however valuable that civil partnership has been to thousands of people like me, the fact is, it isn’t a marriage and you only have to ask the question of heterosexual couples whether they would like their marriage to be called a civil partnership and they would be forbidden from entering a marriage, to realise that it is different and that that difference matters.

“The real question is, ‘if we value marriage so much as an institution in our society, and we should and we do, if it is an institution that allows two people to express a lifelong commitment to each other in public, to say that they’ll look after each other, that they love each other, why is that institution not available to same sex couples in the same way it is to straight couples?’

Mr Herbert also supports religious bodies being able to offer weddings for gay couples, a controversial omission in the government’s proposals among liberal faith groups and a cause for concern among those which do not wish to solemnise gay marriages.

The Out4Marriage campaign’s own response to the public consultation strongly recommended permissive religious marriage laws.

Mr Herbert said: “After all, marriage is, in part, a civil institution, it need have nothing to do with religion, although I believe, on grounds of religious freedom, if churches wanted to offer a same sex marriage, then they should be allowed to do so.

“Equally, no church should be forced to offer a same sex marriage or some kind of ceremony against their wishes.”

“I think that society is changing and public opinion is changing, a substantial majority of people now support same sex marriage and I therefore think it’s time to change the law and reflect that change in opinion. For me, this is nothing more, nor less than a simple matter of equality and that’s why I’m Out4Marriage, are you?”

Speaking for the Out4Marriage campaign, Harry Fox Davies said: “The support of these senior members of Government and Opposition demonstrates the cross party consensus for legalising same-sex marriage.

“As Nick Herbert says, the difference between civil partnerships and full marriage matters; what we’re talking about here is a bench mark of equality, and we are delighted to have received so much vocal support from all political persuasions.”