The Ulster Unionist leader David Trimble has said his party has a huge task in rebuilding itself after its electoral defeat.
Stepping down as leader: David Trimble
Mr Trimble was speaking publicly for the first time since he announced his resignation at the weekend.
His party lost four of their five seats including Mr Trimble's own in Upper Bann.
He blamed republicans and the government for not implementing the Good Friday Agreement fully.
And he warned the new Secretary of State, Peter Hain, would be a failure if he continued on the same course.
"I have to tell him (Peter Hain) that he will be a failure as secretary of state for Northern Ireland if he continues on the approach that he outlined on radio this morning, because he is still making the same mistake that the government has made over the course of the last number of years.
"He might also like to ask himself what other unionist leader is going to make an effort to implement the Agreement when they see what has happened to the one leader who did unambiguously endeavour to do so."
Mr Trimble said he believed the electorate had voted for stalemate in its choice of parties.
But he said he had no regrets about how he had conducted himself in the political negotiations up to and since the Good Friday Agreement.
"I have no regrets about the strategic decision, or the approach, or about the fundamentals of the Agreement," he said.
"I'm quite sure that the future development of Northern Ireland will be based on that Agreement, give or take a little bit here or there."
He said the UUP "tried too hard to implement the Agreement", and that republicans had failed to do so.
In a barbed reference to former party leader Lord Molyneaux he said he could promise his successor that he would treat them better than his predecessors had treated him.
Mr Trimble looked emotional as the UUP president Lord Rogan paid tribute to him.
Reflecting on his time as party leader, he said: "There is no security of tenure in politics. You are at the mercy of the electorate all the time and you're also at the mercy of events.
"I think I had a good innings in terms of what we managed to do. I am proud of what we did. I am proud of the progress which we achieved.
"If I think back to Northern Ireland 10 years' ago and look at Northern Ireland today, I could say that there is a darned good balance sheet there."
While the DUP had made significant gains at the polls, Mr Trimble said the party's Free Presbyterian values were not reflected by the broader unionist community.
"Unionism needs the Ulster Unionist Party," he insisted.
A meeting of the 100 strong Ulster Unionist executive is likely to take place in about a week.
This will be followed by a special meeting of the larger Ulster Unionist council in about a month which will elect a new leader.
Meanwhile the UUP's sole remaining MP, Lady Sylvia Hermon, said she might be interested in running for the leadership.
Speaking to the Irish broadcaster RTE on Sunday, Lady Hermon, the MP for North Down, signalled that she was interested in the position of leader.
Lady Sylvia Hermon: The Ulster Unionist's sole MP
However, she said she had to think of her two young children, as well as her husband Jack, the former RUC chief constable, who is suffering from Alzheimer's disease.
"But I care for the party. I care desperately for the future of Northern Ireland so I will think carefully over the weekend and decide at the beginning of the week what I am going to do," she said.