The power to call a unity referendum in Northern Ireland cannot be left entirely in the hands of the North’s Secretary of State, even though it is laid down in the 1998 Belfast Agreement, Taoiseach Michael Martin has said.

Emphasising that Dublin and London must move “in lockstep”, Martin insisted that all big decisions on constitutional issues could not be taken by London alone.

The 1998 Belfast Agreement lays down that the British government’s minister for Northern Ireland shall call a referendum if, in their view, they believe that a proposal to unify Ireland would be backed by a majority of northern voters.

Pointing to the vagueness of the language used then, Martin told the BBC Borderlands podcast: “It is not satisfactory that it’s kind of loosely put as a judgment call. How do you measure that, and so on, are legitimate issues that have to be teased out.”

Talks involving Dublin and London and all of the Northern Ireland parties should be part of “the teasing out” of when, or whether, the necessary threshold providing for a referendum has been met.

Declining to use the phrase “Border poll”, Martin said the referendum, if held, will decide the future of the island and must honour former SDLP deputy leader Seamus Mallon’s declaration that “it was about time we learned how to share this space”.

“That does inspire me … we need to broaden and be generous in how we approach that,” said Martin.

Partisan advocacy by those for unity will not succeed, he cautioned, since the concepts of parity of esteem, respect for different identities that were laid down in the agreement must be respected: “We need not lose that sense of mutual respect.”

Responding to the mini-controversy caused by British prime minister Andy Burnham’s declaration in Belfast that unity was “off the table”, the Taoiseach cautioned against the more extreme reactions to Burnham’s words.

Saying that Burnham had said “nothing different” that would affect the calling of a referendum, Martin said he welcomed his commitment to the principle of consent laid down in the agreement.

Advising against a hasty referendum, Martin said there has to be engagement with unionists that convinces them about the benefits of unity, rather than attempting to browbeat them into a united Ireland.

Nobody who experienced the Troubles wants to go back, he said: “They don’t want tensions at a level … And that can happen if this is handled wrongly.”

Calling for reasoned debate, he said: “We should stop that kind of name-calling on all sides.”