Campaigners will hand a letter to the British Prime Minister today demanding the disclosure of photographs and film footage shot during the Bloody Sunday killings 31 years ago.
The Bloody Sunday Organising Committee has accused the British Ministry of Defence of withholding the photographs and footage from the Saville Inquiry, which was set up to investigate the killing of 13 unarmed civilians by British soldiers in Derry on January 30, 1972.
Spokesman Jim London said: "It is a disgrace that almost five years into this public inquiry that the MoD has refused to disclose the helicopter footage and photographs that they took on Bloody Sunday.
"We are asking that Prime Minister Blair direct the MoD either to hand this material over to the inquiry and the families or to provide explanations as to what has become of this evidence."
The Saville Inquiry will not sit today as a mark of respect on the anniversary of the 1972 atrocity.
A minute's silence will also be held today at the Bloody Sunday memorial in the Bogside area of Derry, where the 13 civil rights marchers were gunned down exactly 30 years ago. A commemorative march at the scene of the killings will be held on Sunday.