Speaking to the Fine Gael Ard Fheis, or annual conference, in Dublin, he said: "Throughout the ceasefire the IRA continued to train volunteers, continued to target people, continued to single out individuals for potential assassination, continued to tolerate punishment beatings".
He said Sinn Fein must come to a "negotiating table from which threats have been banished" and went on: "There cannot be a situation where peaceful parties feel under threat from others who insist on their right to approve or support violence if things at the negotiating table do not go their way."
Mr Bruton, who is due to meet David Trimble, leader of the Ulster Unionists, tomorrow, said Unionists had lost an opportunity by not speaking to Sinn Fein during the ceasefire. But he went on to make an uncompromising attack on the IRA.
"Serious engagement in a peace process means that you change your strategy as well as your tactics," he said "This did not happen in the republican movement during the last 18 months."
Meanwhile the Ulster Unionists claimed that an invitation to Mr Trimble to be a guest of President Bill Clinton at the White House St Patrick's Day celebrations this week is a sign of the growing isolation of Gerry Adams, president of Sinn Fein, who has not been invited.
John Taylor, deputy leader of the Ulster Unionists said: "It is a dramatic turn of events."Reuse content