Sinn Féin and the SDLP are due to meet officials from the North's Human Rights Commission today to raise their concerns about the behaviour of its chief executive, Brice Dickson.
Professor Dickson is currently under pressure to resign over a letter he sent to the former RUC chief constable disassociating himself from a case the commission was taking against the police.
The case related to the policing of the loyalist protest outside the Catholic Holy Cross primary school in north Belfast two years ago.
The Human Rights Commission was funding a case taken by a parent who accused the police of failing to protect her daughter's right to attend school in safety.
However, Professor Dickson wrote to Mr Flanagan, the then chief constable, saying he did not believe the policing of the loyalist protest was a breach of human rights law.