Relatives of those murdered in the Omagh bombing have met British MPs as part of their campaign for a public inquiry.
Michael Gallagher, whose son Aiden died in the 1998 blast, said the security forces had fallen short in their bid to bring those responsible to justice.
He demanded a cross-border public inquiry into the atrocity.
He told Westminster's Northern Ireland Affairs Committee, sitting at Stormont, that over the past five years, over 40 terrorists, including al Qaeda and Muslim extremists have been put in jail for planning or assisting terrorist acts.
He used prosecutions after the July 2005 London bombings as an example.
'With the Omagh intelligence there's so many discrepancies here that we are at a loss as to why these bombers and the people associated with them were not put in jail,' he said.
The families of the 29 people who died in the Real IRA bomb attack briefed the Westminster committee at Stormont .
The families want a cross-border public inquiry to consider security force intelligence before the explosion, and the failure to secure convictions.
Mr Gallagher said: 'Over the past 10 years the families have been taken to hell and back and there needs to be some degree of closure in Omagh'.
'We feel that the best way forward is a full cross-border public inquiry.'
