Lord Kilclooney was UUP deputy leader from 1995 to 2001, while Brid Rodgers had the same position in the SDLP from 2001 to 2004.

Speaking on Radio Ulster’s Talkback, both said that the decisions would be good for the parties and for Northern Ireland as a whole.

“I think both the SDLP and the Ulster Unionists will benefit from this courageous decision to go into opposition,” Lord Kilclooney said.

“Ulster needs an opposition and we’ve got a cross-community opposition now that will really make the assembly much more interesting for the public and individuals like Eamonn McCann emerging from the middle of the last century will make it an even more colourful arena.”

Mrs Rodgers said: “I think the SDLP have remained true to their beliefs, to their mandate and to everything that they had aspired to from the beginning.

“It’s the right thing to do and I want to congratulate Colum Eastwood.”

‘Not reneging on agreement’

She said the SDLP had been accused of reneging on the Good Friday Agreement, but that was not the case.

“You have to remember that the Good Friday Agreement was changed on a number of occasions by the DUP and Sinn Féin,” she said.

“The vision of John Hume, the aspiration of John Hume, for a real partnership power-sharing executive which would heal the divisions of the past and help us to grow together has not happened, particularly in the last nine years.

“There hasn’t been real partnership in the last nine years, it has been a power-sharing carve-up.”

Lord Kilclooney said the Northern Ireland Assembly had become “boring” to the public.

“It wasn’t creating the interest among the public in Northern Ireland that it needs and democracy wasn’t really taking place,” he said.

“Now we’re going to have a cross-community executive and we’re going to have a cross-community opposition and I think that is very good for Northern Ireland.”

Only the DUP and Sinn Féin remain in the Northern Ireland Executive and both parties have criticised the UUP and SDLP for going into opposition.