Former SDLP deputy First Minister Seamus Mallon has said he was "pleasantly surprised" by Peter Robinson's suggestion of holding a poll on Irish unity every generation.
"It is interesting and a very good thing that Peter Robinson is thinking beyond the box," Mr Mallon said.
"I hope his words will encourage others to start considering things in a similarly positive way."
Former DUP leader Mr Robinson last week suggested that holding generational border polls was a way of stabilising politics in Northern Ireland.
Delivering a lecture at Queen's University, he said such an approach would help make the constitutional question less disruptive to local politics and the prospect of a referendum less threatening.
He stated he would be very confident that citizens would choose to stay within the UK.
Mr Mallon told the Belfast Telegraph: "I was pleasantly surprised by what Peter Robinson said.
"I very much welcome it as it shows foresight. I hope it will now prompt others to begin looking to the future and planning for it."
But both former UK Unionist leader Bob McCartney and TUV leader Jim Allister said Mr Robinson's suggestion could not be welcomed by any unionist.
DUP MPs Gregory Campbell, Sir Jeffrey Donaldson and Sammy Wilson have also distanced themselves from the generational border poll proposal.
Mr McCartney said: "I always thought that Peter Robinson was an excellent tactician but that he lacked strategic vision and I believe his proposal proves that."
The former North Down MLA said Mr Robinson's definition of a generational poll was unclear. "Is it every 18 years or every 25 years?" he asked.
Mr McCartney continued that the Brexit referendum proved that such polls generate enormous instability.
"They aid those who thrive on instability," he said. "Having one here along the lines Peter Robinson proposed would keep every generation on the edge.
"And the temperature would be turned up one or two years in advance of the vote."
Mr McCartney stated he was at a loss to see what unionists had to gain from the proposal which he believed benefited only republicans.
"Sinn Fein hoped that the Belfast Agreement would be a transition process leading to a united Ireland. They have realised that isn't happening.
"Rather, the Agreement has brought about a degree of stability to Northern Ireland, particularly economic stability and investment," he commented.
"Deep down, Sinn Fein realises that its strategy hasn't worked. So the party is running with the idea of a border poll because it would thrive on the instability that would create."
Mr Allister said he failed to understand how any unionist could "talk up" the idea of holding a border poll.
"That is the battle cry of Sinn Fein," he commented. "Why on earth would any unionist give it credence?
"To be even debating the mechanics of this is unhelpful to unionism. It is beyond me why Peter Robinson would want to give legs to this idea."
Mr Allister said the "subtext" of the former DUP leader's speech was: "If I was in charge of the party we wouldn't be in this mess".
He added: "It was pretty obvious that Arlene Foster was the target of some of Peter Robinson's rebukes."
The main focus of the former First Minister's lecture at Queen's were his reflections on how to restore a stable power-sharing administration. Mr Robinson, who was recently appointed an honorary professor of peace studies at Queen's, warned that community division in the region was "accelerating" and suggested violence could reignite if the political stagnation continued.
"We are at risk of awaking the slumbering hostilities that we had all hoped would never again be aroused," he said.
He described the talks process to restore devolution in Northern Ireland as a "train wreck" and called on the DUP and Sinn Fein to go beyond their narrow party interests. Mr Robinson continued that one of the hardest tasks would be for the leaders to sell any deal to their parties.
"Let's be clear, not all of your colleagues will want to make the necessary concessions," he said.
"That's where leadership comes in.
"It will be a career-defining moment.
"Make no mistake about it, your leadership will be on the line. If they reject your recommendation, they are rejecting your leadership. So fight tooth and nail for it."
Working together, Northern Ireland's two communities could achieve great things, he added.