Northern Ireland's first minister Ian Paisley is to stand down from the post in May, he has announced.
He also said he would be resigning as leader of the DUP, a party he has led for almost 40 years. He will continue as MP and MLA for North Antrim.
Mr Paisley, who will be 82 in April, became first minister in May 2007 following the suspension of direct rule after a period of five years.
Peter Robinson, the party's deputy leader, is expected to take his place.
"Unionists are no longer protesting against a London/Dublin deal with which we have no truck," Mr Paisley said.
"We are inside the building administering British rule over Northern Ireland."
Mr Paisley stood down as moderator of the Free Presbyterian Church in January amid concerns about his dual role as the church's leader and first minister.
"I came to this decision a few weeks ago when I was thinking very much about the forthcoming investment conference and what was going to come after the conference," he said.
"I thought that it is a marker, a very big marker and it would be a very appropriate time for me to bow out."
HAVE YOUR SAY
Whether or not you agree with Paisley, there is an honesty that marks him out
Phil Dee, Wales
While it is expected that his current deputy Peter Robinson will succeed him as party leader, Mr Paisley said it was up to the DUP to make the decision.
"This is not Apostolic succession and I have no right to say who will succeed me," he said.
"The person will succeed me when the mark is on the paper and the ballot is cast."
Mr Paisley's announcement followed speculation that senior party members were unhappy about the appointment of his son, Ian Paisley Jnr, to the Policing Board.
Last month, Mr Paisley Jnr resigned as a junior minister in the Northern Ireland Executive.
His resignation followed criticism over his links to developer Seymour Sweeney and controversy over lobbying activity.
However, Mr Paisley said the recent controversy had nothing to do with his decision to step aside.
"I never even considered it. I felt that my son was very badly treated," he added.
"I am not a fool, people who thought that they could get at me, got at him.
"They thought they could damage me by the damage they sought to take out on him, but that did not move me."
Deputy First Minister Martin McGuinness said his ministerial colleague's move was not unexpected.
"The historic decision he took to go into government with Sinn Fein has changed the face of Irish politics forever," he said.
Prime Minister Gordon Brown said Mr Paisley had made a huge contribution to political life in Northern Ireland and the United Kingdom.
"The whole country values and admires the manner in which he has led as first minister," he said.
Irish Prime Minister Bertie Ahern said he did not believe Mr Paisley's decision would affect the future of the power-sharing government.
"I honestly believe that (devolution) will last because I believe there are very pragmatic people in all of the parties," he said.