Sinn Fein has effectively torpedoed new proposals for the appointment of senior Stormont officials as the row over the appointment of Mary McArdle takes another twist.
The party said it was not prepared to endorse the return of security vetting - which is at the heart of suggested rules drawn up by DUP minister Sammy Wilson.
"Security vetting has been used in the past to make positions in Government, including those in the senior Civil Service, the preserve of one section of the community," a statement said.
"Sinn Fein will not accept the application of such discriminatory employment practices in the appointment of special advisers or anyone else."
The rebuff came after it emerged Mr Wilson is still aiming to force Ms McArdle out of her job by making his proposals apply retrospectively.
Ms McArdle could not become a senior Stormont aide under the suggestions which have just been sent to other Stormont ministers.
The updated rules would mean the adviser to Culture and Arts Minister Caral Ni Chuilin would not have met security requirements and been told she was not suitable for appointment.
Controversy has raged since it was learned Ms McArdle, who was jailed for her role in the 1984 IRA murder of Resident Magistrate Tom Travers' daughter Mary - who was shot with her father as the family left Mass - had been given the senior position.
First Minister Peter Robinson said it was a "mistake" and tasked Mr Wilson with examining the arrangements to prevent a recurrence of the situation.
A spokesperson for Sinn Fein said, however: "The code of practice for appointment of special advisers was agreed by the Executive 12 years ago. It includes acceptance that each minister has the authority to appoint his/her special adviser.
"Any change to these arrangements will require Executive approval."
Meanwhile, Traditional Unionist Voice MLA Jim Allister has asked the Northern Ireland Ombudsman to investigate if the March 2011 code of practice on the appointment of special advisers - issued by Mr Wilson's own department - was complied with in relation to Ms McArdle.