Omagh bomb victims are expected to demand a timetable for setting up a cross-Border investigation into the atrocity during talks today with the Government.
Relatives of some of the 29 people killed in the "Real IRA" massacre are meeting Minister for Foreign Affairs Dermot Ahern in Dundalk today.
Although south Armagh electrician Seán Hoey has been charged with the August 1998 murders, campaigners want an inquiry into how police on both sides of the Border handled the investigation.
Opposition party leaders have criticised the government for failing to publish in full a report it commissioned into Garda intelligence handling at the time of the attack.
Michael Gallagher, whose son Aidan was among those killed in the attack, insisted the Irish authorities should back their campaign in the same way they lobbied for a new tribunal into the 1972 Bloody Sunday shootings in Derry.
He claimed: "They are applying double standards by not affording the people of Omagh the same justice and fair treatment.
"If they want to use the delaying tactics of the Hoey trial and our civil action [against five men suspected of plotting the bombing], surely that does not stop us making preparations.
"I'm taking it as a foregone conclusion that you cannot deny the people of Omagh a full inquiry," he said.