Sinn Féin West Tyrone MP Órfhlaith Begley said the High Court recommendation was a tribute to the “determination and courage of the families of all those killed in the atrocity and their long campaign for truth and justice”.
“The judge’s comments that there is a real prospect the bombing could have been prevented will undoubtedly add to the distress of the families and leave them with further questions,” she said.
“That is why it is vital that the British government act on the judge’s recommendation and immediately move to announce a full, human rights compliant investigation into the exact circumstances of what happened.
“Grieving families should not have to face any further delays or face any more obstacles when it comes to finding out the truth about the deaths of their loved ones.”
SDLP leader and Foyle MP Colum Eastwood said the courage of the families of Omagh victims is “inspiring but they deserve the whole truth of what transpired”.
“We support their campaign for a full public inquiry into what happened,” he added.
Ulster Unionist MLA Mike Nesbitt, a former victims’ commissioner, said the full ruling will need very close scrutiny.
‘Work of the terrorists’
“Whatever detail is contained in the full ruling, the fact remains that the Omagh bomb was the work of the terrorists who chose to make it, transport it and detonate it in a market town on a busy August Saturday afternoon,“ he added.
Taoiseach Micheál Martin has promised that the Government will consider a probe into the atrocity to establish if the attack could have been prevented.
“That was the single worst atrocity that occurred — it was appalling. But the responsibility rests with those that committed that foul act,” he said.
“So many people lost their lives — that said, there is an obligation on the (Irish and British) governments to examine what could have been done and if anything could have been done to prevent the atrocity with a view to informing future practice.
“I am in no doubt that evil people did that. It was an appalling, reckless act. It gave such heartache and broke so many families with the totally needless loss of life.
“We were well on the way to the peace process at the time and we should never lose sight of those who were ultimately responsible in the first instance — those who perpetrated this awful crime and thought up the idea of planting that bomb.
“We can never lose sight of that and they are fundamentally guilty of murdering so many people.
“But the State must always self-reflect in terms of how it acts to protect innocent people. I have just heard the news of the conclusion and there is an obligation on both Governments to consider that judgement.”
‘Careful consideration’
Mr Martin said he believed wholeheartedly in full openness and transparency. However, he said, aspects of the ruling will need careful consideration.
“We are going to analyse that judgement and do what is necessary in terms of the citizens on the island of Ireland.
“I always stand ready to have an open book in terms of any atrocity that is committed which has a cross-border dimension to it.
“In terms of following through in any way we can through the provision of information or the need to vindicate the rights of citizens. I am very open in terms of how we proceed with this. We have got to examine the options that are available to us.”
Michael Gallagher, whose son Anthony was killed in the bombing, said the enormity of the finding has yet to sink in.
“We would just call on the Government not to delay the suffering we have already went through over the past 23 years,” he told RTÉ.
“Do not go into an appeal process. Work with the families and move forward. Because we are not the terrorists here, we actually supported the government, we support the police, we support the intelligence service and we’ve asked the government to work with us.
“But that was not the case, so we’re here. What was a pleasant surprise today was that the judge talked about the Irish government in a cross border inquiry. We’ve felt that there should have been a cross border police investigation in 1998.”
Wave, the North’s largest cross-community victim support organisation, said the court finding “is a stark reminder that a line cannot be drawn under murder”.
“An amnesty is just wrong,” a spokesman said.