The Fine Gael leader, Mr John Bruton, has warned of the danger of paramilitary groups using violence systematically to influence the Northern talks while their political representatives stay at the negotiating table.
Addressing a conference of young politicians from Ireland and Britain on Saturday, he said: "It cannot be left to the UDP simply to assert that they have opposed violence by the UFF without an accepted independent system of verification. I believe that, in this instance, they have done so. But the precedent of independent assessment must be established now.
"The rigorous application of the Mitchell Principles," he said, "is the last line of defence against formal acceptance of violence or threats of violence as accepted methods of politics in two of the oldest continuous democracies in Europe, namely Ireland and the United Kingdom." Young politicians from 16 Irish and British parties were represented at the conference, which was organised by the youth wing of Fine Gael and held in the British embassy residence in Sandyford, Co Dublin.
Other parties represented were Fianna Fail, both the Irish and British Labour parties, Democratic Left, SDLP, Sinn Fein, the Progressive Unionist Party, the Alliance Party, Plaid Cymru, the Scottish National Party, the Conservative Party, the Liberal Democrats and the Irish and British Greens.
The event was notable for the presence of four representatives from Sinn Fein, the first time the party has attended any event at the British embassy. None of the three mainstream unionist parties attended.
The organiser, Mr David Murphy of Fine Gael, said it was "a kind of Council of the Isles at youth level".
Mr Peter Kelly of the SDLP said most parties agreed that some kind of relationship between the two parts of Ireland, England, Scotland and Wales would have to be a part of any enduring agreement. Only Sinn Fein insisted on an agreement strictly within an all-Ireland context with no British involvement.