About 500 people marched through central London on Saturday to commemorate the 27th anniversary of Bloody Sunday.
The event was disrupted for a short period when protesters, believed to be from the British National Front, shouted abuse at the marchers near Trafalgar Square. Police intervened and arrested one protester for breach of the peace.
Members of the Bloody Sunday Justice Campaign, which organised the march, handed in a letter for the British Prime Minister, Mr Tony Blair, at 10 Downing Street, in which they expressed concern that the new inquiry, led by Lord Saville, could turn into "a second whitewash".
"Over the last 30 years, almost 400 families have experienced the deaths of loved ones by the actions of the British army and RUC. Each of these deaths needs to be looked at," the letter continued.
Speaking at the commemorative rally following the march, Mr Gerry Kelly, a Sinn Fein Assembly member for North Belfast, stressed the importance of "achieving justice for all victims of the conflict".
He said no grouping had a "monopoly on suffering and grief" and called on the British government and unionists to "treat with equal respect all those relatives who lost someone in this conflict.
"There is no excuse for some horrific acts that have occurred on all sides and that includes the IRA, but if we are to achieve a lasting peace, the healing process must be inclusive." He accused the North's First Minister, Mr David Trimble, of trying to refuse nationalists access to "equality, human rights and a just policing service" by excluding Sinn Fein from the executive.
"We have the mandated right to our place on the executive. Sinn Fein voters and their elected representatives are as worthy of acknowledgement and inclusion as every other voter," Mr Kelly said.
At the same rally, a British Labour MP, Mr John McDonnell, accused unionists of using the issue of decommissioning as a "delaying tactic".
"We will not allow the career prospects of Mr Trimble to block us on our path to peace. We will remain firm in the search for peace, but with peace we want truth and we want justice," he said.