Ulster Unionist leader Mike Nesbitt has announced he is to step down after his party's poor showing in the Assembly election.
His announcement comes after the UUP failed to make any ground on the Democratic Unionists and after losing a number of high-profile seats.
In a news conference this evening, he said he had been reflecting on the results and said the "buck stops here".
For the past three months, he said, he had been criticising another party leader for not taking responsibility for actions that occurred on their watch.
He said it would be the "height of hypocrisy" if he did not take full responsibility for his party's poor election performance.
Mr Nesbitt said: "I led into this election. I was the one who argued it should be a referendum on RHI and on ten years of the DUP and Sinn Féin leading our Executive government.
"I am the one who suggested in a normal society people would vote on performance and that the DUP and Sinn Féin did not earn another mandate.
"And I'm the one who said this should be Northern Ireland's first post-sectarian election based on the economy and education, health and housing, and that I had a different vision."
He added: "But the electorate disagreed. They certainly did not give me a mandate big enough for me to feel justified in continuing in this position, so I shall not continue in this position."
He said he will stay in the post until a successor is elected and Mr Nesbitt will remain an MLA for Strangford.
Mr Nesbitt said his real regret was that Northern Ireland society appeared to have emerged from the election more polarised.
He reflected that his vision of a society where unionists could voice support for a nationalist without suffering at the polls had yet to be realised. "But we will get there," he insisted.
"Someday Northern Ireland will vote as a normal democracy. We will vote in a post-sectarian election but it's now clear it will not happen during the duration of my political career."
He had led the UUP since 2012 and pledged to deliver a new middle-ground politics for the people of Northern Ireland.
He attempted to build a cross-community coalition in opposition to what he felt were the failed politics of the DUP and Sinn Féin alliance.
But on a night of disappointments his party lost stalwart former Stormont minister Danny Kennedy as well as other senior members and failed to close the seats gap with the Democratic Unionists.