The Nobel peace prizewinner John Hume is to stand down as leader of the SDLP.

The 64-year-old Northern Ireland MP is set to announce a further reduction in his workload following concerns over his health. He is expected to continue as the MP for Foyle - the seat he has represented since 1983.

Hume, who has been the party's leader and a member of the European Parliament since 1979, is credited as having begun the talks with Sinn Fein which led to the Good Friday Agreement.

He was jointly awarded the Nobel Peace Prize with David Trimble in 1998. The son of a shipyard riveter, his political career was born with the Catholic Civil Rights movement in 1968.

He stood down from the Northern Ireland Assembly earlier this year citing a heavy workload and health concerns.

The outgoing leader said the decision to stand down was a difficult one. "I was leader of a great team of people, all of whom have been totally committed to peace and stability on our streets," he said.

Prime Minister Tony Blair paid a warm tribute to Hume's efforts in building peace in Northern Ireland."John Hume has played a huge role over many years in the Northern Ireland peace process and in helping to take the gun out of Irish politics. His vision was instrumental in establishing the process that has led to the Good Friday Agreement and I would personally like to thank him for his tireless efforts to realise that vision," Blair said.

Irish Prime Minister Bertie Ahern said Hume was "a true Irish hero".

"In times when violence and hatred have threatened to overwhelm those who sought a political solution, the name of John Hume became synonymous with the refusal to yield to those forces of hatred," he said.

"The philosopher, architect, and ultimately symbol of peace, John Hume never faltered in his insistence that dialogue was the only way forward, never tired in his efforts to persuade others to come round the table, never failed in his belief that a peaceful solution could be found to the problems of this island."

Sinn Fein president Gerry Adams paid tribute to Mr Hume's work during the peace process. "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," he said.

The SDLP's deputy leader Seamus Mallon, who is also acting deputy first minister, is tipped as the man most likely to succeed Hume. South Down MP Eddie McGrady and Stormont's agriculture minister Brid Rodgers are also possible candidates.

Mallon said the announcement would return attention to the peace process once again. "It is an end of an era in one way and a beginning of an era in another way, but I believe that coming at a crucial time it will focus minds yet again on the enormity of what we have to do here, the enormity of what has been done and the remarkable potential for the future that we haven't yet realised," he said.