The Northern Ireland Human Rights Commission has been accused of "gravely undermining" public confidence in its work and failing to take action to set this right.
Sinn Féin has written to both the Northern Ireland Office and the commission raising concerns over the work of the organisation in the wake of a series of controversies.
Sinn Féin Equality and Human Rights spokeswoman Bairbre de Brun accused chief commissioner Brice Dickson of not dealing "satisfactorily with these concerns about the way the commission has developed under his stewardship".
The commission was a key creation of the Good Friday Agreement, but it has faced criticism over its handling of a case relating to the Holy Cross school protest as well as its plans for a Bill of Rights for Northern Ireland.
Three commission members have resigned claiming the Bill proposals risk undermining ex-isting fair employment laws.
Mr Dickson has also confirmed that after the commission agreed to fund a legal challenge by a Holy Cross parent to the policing of the protest he wrote to the then chief constable Sir Ronnie Flanagan revealing that he did not believe the case had merit.
The controversy reached a height in July when both Sinn Féin and the SDLP questioned Mr Dickson's continued leadership of the body.
Last night (Wednesday) the commission's chief executive Paddy Sloan responded to the Sinn Féin comments.
"The criticisms and challenges put to the commission are still under active review and are informing our ongoing work and strategic planning processes," he said.
In a further development, Ms de Brun has written to NIO human rights minister John Spellar expressing concern at the process used to appoint commission members.
The NIO currently oversees appointments, handling the process as it would with any other public body.
Sinn Féin has called for an independent appointment process based on the 'Paris Principles' which recommend that appointments to a human rights organisation must not be handled in the same fashion as other public bodies but should instead be made with reference to the human rights experience of applicants.
An NIO spokesman said it was aware of the concerns over the appointment process, adding: "Ministers are currently considering the best way forward."
