Martin McGuinness has been challenged by Arlene Foster to reveal what she claims he knows about the Enniskillen bomb atrocity.
Ms Foster, Northern Ireland’s trade and industry minister, said there had been speculation for decades that it was the IRA from Derry which was involved in the 1987 bombing which killed 11 people as they gathered at the town's cenotaph.
The Presidential candidate has admitted being in the IRA in Derry but insists he left the organisation in 1974.
Last night on RTÉ’s Prime Time he said he was "ashamed" about republican involvement in the no-warning attack.
Today Ms Foster called on Mr McGuinness, who has stepped aside as deputy Northern Ireland First Minister because of the presidential contest, to assist the Historical Enquiry Team which is examining the police investigation into Enniskillen.
No-one has ever been charged.
Ms Foster, the DUP MLA for Fermanagh-South Tyrone, said: "If Martin McGuinness really believes the murders that day were shameful then he should have no problem speaking to the HET and answer any questions which they have.
"The speculation for decades has been that the Enniskillen bomb was the work of provos from Londonderry (Derry) where Martin McGuinness was the second in command of the PIRA.
"Rather than proposing an international truth commission to deal with these matters, it would be much more helpful to the healing process if McGuinness was to tell the truth about this incident to the HET."