The ex-Ulster Unionist MLA whose bill paved the way for Mike Nesbitt to create Stormont's first official opposition has backed his former colleagues' decision to stay out of the executive.
John McCallister, who left the UUP in 2013 and lost his assembly seat in last week's election, told The Irish News his former party's move into opposition was a "positive development" that would help normalise politics in the north.
Mr McCallister's remarks came as former UUP leader Lord David Trimble described his successor's decision as a "bold move".
Lord Trimble said in the immediate aftermath of the Good Friday Agreement it was important that all the parties worked together but that this was less crucial as the political institutions matured.
"It is a bold move but it's a move which I think reflects what was always going to be the case," he told the BBC.
"I think bold moves have to be taken now and again and people have to offer leadership."
He said it was ironic of Martin McGuinness to criticise Mr Nesbitt given the Fresh Start agreement's pledge to support measures that would create an official opposition.
"Mr McGuinness and Sinn Féin were party to putting those arrangements [to create an opposition] in place, so it's a bit silly to turn round and complain that it's happened," he said.
"Rather than throwing these negative comments at it, what others parties should be doing is saying: 'OK, let's see if this works.'"
Mr McCallister said he had advocated the UUP going into opposition when running for the party's deputy leadership in 2012.
"I always believed there should be government and opposition and that they shouldn't be the same people," he said.
"If you're in government you should be voting with the government, otherwise it becomes dysfunctional."
The former South Down MLA said he believed the UUP would have secured more than 16 seats in last week's poll had they campaigned on the basis that they would go into opposition if they did not get enough MLAs to secure either the first or deputy first minister's position.
He said he was hopeful the move into opposition would help the UUP – and possibly the SDLP if it follows suit – formulate policies which gave the electorate a choice.
"Moving into opposition is a positive development that will help normalise our politics," he said.
"Overall I believe it's about better government and the incumbents being held to account and I hope the natural direction of travel is to offer an alternative to what the governing parties are doing."
