The call by Christian Concern For Our Nation (CCFON), the lay-arm of the Lawyers' Christian Fellowship, comes amid growing concern over the "serious implications of the regulations on Christian conscience and freedoms".
CCFON is also concerned by "the way in which the Government has abused the normal democratic and parliamentary processes to bring in this legislation, and has stifled debate".
The vigil will take place outside Parliament at Old Palace Yard on Wednesday 21 March, from 7-9pm when the final vote on the regulations will be taken.
Organiser, Andrea Minichiello Williams, said that while CCFON and other Christian organisations have been doing all they can to lobby Government ministers, MPs and members of the House of Lords, what is still needed is prayer for a "miracle" on Wednesday if the regulations are to be halted.
She said: "Baroness O'Cathain is to move an amendment to the Government's motion approve the SORs. She is asking for support to the effect that 'this House, having regard to the widespread concerns that the draft regulations compromise religious liberty and will result in litigation over the content of classroom teaching, and having regard to the legality of the equivalent regulations for Northern Ireland, declines to approve the Equality Act (Sexual Orientation) Regulations 2007'.
"She, and other like-minded peers need our support and prayers, and whatever the outcome, it is vital that history records Christians standing for truth to the very end of the parliamentary process."