Two senior Orangemen will defy the Order's official advice and vote in the House of Lords in favour of gay marriage.
Yesterday, an Orange Order spokesman described Monday's House of Commons vote to legalise same sex marriage as "further evidence of the departure from Christian standards in our nation and of moral decline".
Deputy Grand Master the Rev Alistair Smyth added: "We urge all Christian people to continue to hold true to Christian values and to pray that God in his mercy would turn people to seek the Lord and his ways."
But the Bill still has to clear the Lords where at least two of his own members have pledged to vote in favour of gay marriage.
They are Lord Laird of Artigarvan and Baron Rogan of Lower Iveagh – both members of the Royal York LOL 145. It is one of the oldest lodges in Ireland, founded by soldiers brought to Ireland to fight the United Irishmen in 1798.
Both men are Ulster Unionist peers and last night said they intended to vote for the legalisation of same sex marriage as a matter of moral principle.
"I propose to vote for gay marriage," said Lord Rogan.
"It is an equality issue and I also believe it is a matter of freedom of choice.
"I also think that, quite frankly, a central government has no right to interfere in an individual's liberty and choice."
Asked if he believed same sex couples should have the right to adopt and transfer property as others he replied: "Correct." Lord Laird called for a "programme of education" so that the law could be extended to Northern Ireland by agreement. He added: "It is a matter of freedom and of not of dictating to people how they should live their lives."
This puts them directly at odds with a strongly-worded statement peppered with biblical quotations from the Rev Smyth, a Presbyterian minister from Limavady.
He said: "From a biblical point of view, we believe that marriage is between one man and one woman as evidenced by Genesis 2:24; 'For this reason a man will leave his father and mother and be united to his wife, and they will become one flesh'."
The Rev Smyth fears the right of some churches not to perform gay marriages, written into the new law, "will most likely be challenged under 'equality or human rights' legislation in the European Courts. Therefore, we fear the religious safeguards supposedly built in will soon crumble".
The UUP allows its members to vote freely on the issue according to conscience. Lord Empey, the third UUP peer and also an Orangeman, will vote in line with the Order's official policy.
A member of Eldon LOL 7, the former party leader said: "I believe civil partnership provides sufficiently for individual rights."
He shared the Rev Smyth's fears that, if same sex marriage was introduced, it could eventually lead to churches being forced to carry out the ceremonies.
The DUP is firmly opposed to gay marriage and all its MPs voted against the Bill this week. The party also blocked attempts to extend the legislation to Northern Ireland when the Green Party and Sinn Fein introduced a motion.
The SDLP and Alliance, who have MPs, favour reform – although only one SDLP MP voted.
Last night, the DUP Assembly member Peter Weir said his party believes the legislation is wrong.
"One of the advantages of devolution is that it allows us to prevent such measures being extended to Northern Ireland," he added.
Asked if this meant diverging legally from the rest of the UK, he said: "The UK is a diverse enough society to accommodate difference."