The DUP will not share power with Sinn Fein because the party cannot be trusted, Ian Paisley has insisted.
Mr Paisley said there must be "a new start" in the process
The DUP leader said he would not serve as first minister with a Sinn Fein deputy first minister.
Speaking after a meeting with Prime Minister Tony Blair in Downing Street, he said: "They have had their chance and they have failed."
After their meeting with Mr Blair, Sinn Fein said the Good Friday Agreement was the only basis for future government.
Mr Paisley said the meeting with Mr Blair had been "very helpful and in many ways encouraging".
However, he said there must be "a new start" in the political process and that the DUP would not share power with Sinn Fein.
"I don't see it because I don't trust them and the people don't trust them," he said.
He added: "Mr Adams said today that the IRA would never be disbanded - so if that is his view, then that is it."
The DUP leader said he would not serve as first minister with a Sinn Fein deputy first minister as this was part of the Good Friday Agreement.
"We must have a new beginning and it is not necessary for the government to work that way."
Speaking after meeting Mr Blair, Sinn Fein President Gerry Adams said it was now time to make progress.
"The British Government has a particular role to play along with the Irish government in pressing ahead with the Good Friday Agreement," he said.
"The Plan A has to be implementing the Good Friday Agreement and that is the impression we got from the government.
"We didn't have a post mortem on the Good Friday Agreement - as far as we are concerned the Good Friday Agreement is work in progress."
Northern Ireland Secretary Peter Hain described the meetings with both parties as positive.
"These two parties came out in the general election leading the field - there is now a new era in Northern Ireland politics," he said.
"They need to take their responsibilities seriously to move the whole process forward and create peace, stability and prosperity in the long-term on a stable basis."
He said the government was now waiting on an IRA statement in response to Mr Adams' call for it to follow democratic means.