Northern Ireland's ban on same-sex marriage is having a 'corrosive' impact on society, the High Court heard today.
Counsel for two gay couples challenging the ban claimed they are suffering state discrimination after being marginalised all their lives.
Grainne Close, her partner Shannon Sickles, and Chris and Henry Flanagan-Kane are taking legal action against the Stormont administration in a bid to have the ban lifted.
They were the first couples to enter civil partnerships in the UK.
But they claim that being denied the chance to get married in Northern Ireland breaches their human rights.
Opening their application for judicial review, David McMillen QC stressed how gay and lesbian couples can now wed in the rest of the UK and the Republic of Ireland.
"Northern Ireland stands out as effectively a blot on the map which suggests to the rest of the world (it remains) a backward looking and divided society," he claimed.
Both couples cemented their relationships in civil partnerships at Belfast City Hall back in 2005.
At the time Northern Ireland was the first United Kingdom region to introduce the ceremonies for gay and lesbian couples.
But unlike the rest of the UK, it has still not legalised same-sex marriage.
Proceedings brought against the Department of Finance and Personnel claim the ban breaches entitlements to family life and marriage under the European Convention on Human Rights.
Mr Justice O'Hara is hearing the challenge in tandem with a separate bid by two men who want their marriage in England to be recognised in their native Northern Ireland.
He will then rule on both cases at a later stage.
Mr McMillen described his clients' litigation as an unequivocal challenge to the bar on same sex marriage in Northern Ireland.
He said: "It's nothing less than state discrimination of a class of people who have been marginalised for many years.
"The life-long commitment of these four applicants is the same in every respect as that of any other couple. Those relationships deserve to be recognised as such by having equal access to civil marriage.
"It's demeaning and offensive that their unions have been relegated to a second-class status, namely civil partnerships."
The two couples taking legal action have been kept on the periphery all their lives, the court heard.
"It's intolerable when this comes at the hands of the state," the barrister contended.
"This bar on same sex couples being married in Northern Ireland is perhaps the last great legislative instance of discrimination."
To suffer such treatment based on the very nature of their being and private lives is wrong, he insisted.
He added: "It's corrosive to the very fabric of society that unites us and makes us strong."
Even though Stormont voted last month in favour of changing the law to allow same-sex marriage, the Democratic Unionists used a petition of concern to block any amendment.
That mechanism allows Assembly members to veto any legislation seen as prejudicial to either of Northern Ireland's two main communities.
The court was told it had been "manifestly inappropriate" to use it in this area.
Mr McMillen pointed out: "Thirty Assembly members can veto the will of the democratically elected 108 members of the Assembly."
The case continues.