Former UUP leader Reg Empey and SDLP leader Colum Eastwood have both said Northern Ireland needs to return to the values of the Good Friday Agreement.
The pair were speaking on the BBC’s Good Morning Ulster programme on Monday on the eve of the 20th anniversary of the deal.
The Good Friday Agreement was signed in Belfast on April 10 1998.
Lord Empey said he was “disappointed” that its full potential had not been realised.
He said that Northern Ireland was “a better place” as a result of the deal, which was initially implemented by the UUP and SDLP.
But the agreement was essentially “taken over” by the St Andrews Agreement, he said.
“The agreement which was embraced by people is not the agreement which is now operating.”
Changes made to the agreement at St Andrews undermined the spirit of partnership, he said.
The St Andrews Agreement paved the way for the return of power-sharing to Stormont in May 2007, when Ian Paisley and Martin McGuinness became Northern Ireland’s first and deputy first ministers.
Mr Eastwood said he agreed that “what happened at St Andrews was a disgrace”.
“It led to further polarising of our politics and that has been very damaging,” he said.
“We have to get back to the spirit of the Good Friday Agreement, the idea that it is about partnership and recognising that we have a conflicted space in terms of our politics.
“We have to recognise that compromise needs to happen every day in order to get things done.”
He noted that Sinn Fein had not campaigned for the Good Friday Agreement before it was signed and that he DUP had opposed it.
“What we are left with now are minor issues in comparison to those faced 20 years ago and it shouldn’t be beyond us to get them resolved,” he added.