Mr John Hume was an "enormous force for peace" over the past 30 years, the Northern Secretary, Dr John Reid, has said. He described Mr Hume's commitment to peace and conflict resolution through dialogue and agreement as "unsurpassed".
"He [Mr Hume] has always opposed terrorism from any quarter and consistently made the case for an end to violence and a commitment to the way of democracy and agreement," he said.
"Even in the darkest moments of the past 30 years, John Hume has been a fine ambassador on the international stage for all that is good here - for peace, for tolerance, for the primacy of democracy."
Speaking on Monday, after Mr Hume announced his resignation as SDLP leader, Mr David Trimble said he had never doubted Mr Hume's sincerity in finding an agreed resolution to the North's political problems. His approach to disputed issues had created the space where dialogue between unionists and nationalists became possible.
"At all times, John's voice has been heard because it was never tainted by any covert regard for violence. He deserves credit for his work to redefine Irish nationalism and move it away from simplistic territorial certainties and instead to concentrate on people rather than land and on seeking agreement between the people who actually inhabit the land in question."
The SDLP deputy leader, Mr Seamus Mallon, paid tribute to Mr Hume's "towering leadership" over the past 22 years. "I think that people will recognise the quality of that leadership and historians will evaluate it in a way which, I believe, will show that it has actually changed the course of thinking within Ireland and laid down a basis for political solutions within the island of Ireland," he said.
"We will now as a political party, of course, look to the future recognising the very difficult present."
Lord Fitt of Bells' Hill said he had always considered Mr Hume a friend and he believed that his forte was not on the local political stage. "His place is on the European, the world and the international stage."
The Sinn Fein president, Mr Gerry Adams, described Mr Hume as a "friend as well as a colleague" whose finest hour had been the pulling together of the Belfast Agreement.
"During the course of the peace process, John and I developed a special friendship for the work we did together in laying the foundations for that process and all that stems from it. Undoubtedly John Hume's finest hour came in laying the foundations for the Good Friday agreement."