RUTH Davidson will today tell a Belfast audience that Scotland has become a better place because of equal marriage, as she enters a fraught debate over the issue in Northern Ireland.

The Scottish Conservative leader, in a lecture at Belfast's Pride celebrations, will speak of her own experience as a Protestant unionist, engaged to Catholic Irishwoman, and say that she considers that equal marriage is not about "any one religion, country or community".

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Northern Ireland remains the only part of the UK where gay people can not get married, despite Stormont narrowly voting in favour of equality last year. The Democratic Unionist Party (DUP) deployed what is known as a 'petition of concern', meaning measures require a cross-community majority to pass, to effectively veto the proposal moving forward.

Ms Davidson, at an event organised by Amnesty International, is expected to say: "As a practicing Christian, a protestant and a unionist who is engaged to a Catholic Irishwoman, for me, equal marriage isn’t about one religion, country or community.

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"It is about people in Northern Ireland being afforded the same rights as everybody else. Scotland is a better place today because of equal marriage and I want to take that positive message from our experiences here to Belfast and beyond."

Equal marriage came into force in Scotland in December 2014, after MSPs voted for it by an overwhelming majority the previous February. In England and Wales, the first gay marriages took place in March 2014.

In the Republic of Ireland gay marriage became legal late last year, after 62 per cent voted in favour of amending the country's constitution to allow gay and lesbian couples to marry in a May 2015 referendum.

Colin Hart, Campaign Director of the Coalition for Marriage (C4M) said he welcomed discussion over how to strengthen marriage, which he described as "the most stable form of human relationship".

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However, he added: "C4M and our 40,000 members in Northern Ireland do not believe that ripping up the centuries old definition of marriage, the lifelong union between a man and woman, will achieve this. Rewriting the current law dilutes our understanding of marriage and opens the door to future redefinitions.

"Those arguing for introducing gay marriage must also address the way a small minority of people exploit this debate to attack those with traditional views. Earlier this year in Northern Ireland we saw the terrible situation, where a baker and his family were dragged through the courts by a taxpayer funded quango, for declining to decorate a cake carrying a slogan advocating a changing the law.

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"In England we have seen other cases where those who back traditional marriage have faced being sacked, demoted or having their wages cut. Changing the law in Northern Ireland will lead to many more similar cases."