Former Irish premier Leo Varadkar has proposed a two-stage referendum process for a potential future vote on the reunification of Ireland.

Mr Varadkar suggested an initial vote where people on both sides of the border would decide whether they agree “in principle” with constitutional change, and then a final “confirmatory” ballot once the structures and constitution of the new political entity were designed and presented to the public.

Under the terms of Good Friday peace agreement of 1998, the UK Government is obliged to call a referendum in Northern Ireland if there is evidence of a shift in public opinion in favour of unity. In that event, there would be a simultaneous vote in the Republic of Ireland.

The peace accord does not currently envisage a two-stage process as suggested by former Fine Gael leader Mr Varadkar.

The ex-taoiseach, who stepped down earlier this year, outlined that idea and a series of other proposals as he addressed schoolchildren at an event in Londonderry hosted as part of the SDLP’s New Ireland Commission initiative.

Mr Varadkar also urged all parties contesting the forthcoming general election in the Republic of Ireland to make unification an “objective” rather than just an aspiration.

The TD, who is not seeking re-election, said he would like to see all parties dedicate a section of their manifestos to the issue.

He said the next Irish government should boost funding in the state’s existing Shared Island initiative and also set up its own commission to examine reunification.

He also insisted that a new Ireland would have to be “co-designed” along with those of a British identity.

Mr Varadkar suggested the Irish parliament could sit at Stormont in Belfast for parts of the year in the event of unification.

He also proposed that the unified state could have a president and vice-president, one of whom would be from the unionist/British tradition.

The former premier said a unified Ireland would also need to strike international defence agreements and partnerships in order to protect its seas and airspace.

In regard to his proposed two-stage referendum, Mr Varadkar acknowledged that it could prove controversial.

“One idea that I’ve suggested, and it might be a terrible idea, but I think it’s worth thinking about is a two-stage process, one where people vote on the idea in principle, then we have a convention that works out the details and the new constitution, and people get to do a confirmatory vote,” he said.

“A lot of people think that’s a bad idea, because they want the clear question first, but it’s not one that I think should be thrown out. It’s something I think should be thought about.

“And I’m conscious that the new prime minister, Keir Starmer, actually advocated this approach in relation to Brexit, called for a second vote on the deal. So it’s not an entirely crazy idea, and one that’s been suggested before.”

While schools from across Derry were invited to Thursday’s event at the city’s Playhouse, only schools from the Catholic education sector attended.

Mr Varadkar acknowledged that many unionists and loyalists do not wish to engage in discussions about Irish unification.

He said he would take a similar stance if asked to consider the Republic of Ireland re-joining the UK.

But he said a yes vote in the initial “in principle” ballot might persuade sceptics to get involved in the process of designing the new state.

“There are people who are very strong and avowed unionists who will never want to have this conversation, just as I wouldn’t want to engage in a conversation about the Republic of Ireland joining the United Kingdom, I wouldn’t be interested in that, so that is a real difficulty for us,” he said.

“But I do think there are people who come from a Protestant background, or come from a Protestant/unionist/loyalist background who don’t necessarily vote for the unionist parties anymore, who might be interested in engaging.

“They might vote Alliance, they might vote SDLP or Green, or they might not vote at all.

“So I do think there are people, and I’ve met them, who are interested in having this conversation, and they’re coming from a background that traditionally would be Protestant or unionist, but it is one of the ideas why I think there is some merit in considering a two-stage referendum, because if we had the first stage and people north and south voted for unification in principle, I think you might then get a larger number who would accept the democratic outcome, and then might be willing to engage in the co-design of what that new Ireland looks like.”

Mr Varadkar said the concept of “accommodating” people from a British identity in a new Ireland did not go far enough.

“It’s really important that we don’t just try to accommodate them in a new Ireland, but that we try and design the new Ireland with them, so that’s their home too,” he said.

“Somebody said to me once that they really don’t like the word ‘accommodation’, because accommodation, it’s like a hotel, or it’s a B&B, it’s somewhere where you get to stay, but it’s not really your home.

“And what we have to do to make sure a united Ireland works is to make sure that we co-design this, at least with those who are willing to talk to us about it, and we make accommodations or make changes and concessions that I think would work.”

Mr Varadkar said while he felt that unity would be achieved in the coming decades, he cautioned it was by no means certain.

He said that was why preparation was vital, as he warned that a no vote in any referenda would knock the issue “off the agenda for a long time”.

The ex-Fine Gael leader said unification was becoming a more attractive prospect for a variety of factors.

He said the opportunity of Northern Ireland re-joining the EU through unification was one pull factor.

Mr Varadkar also said the economy, health service, childcare support and welfare system were all in a better state in the Republic of Ireland than in Northern Ireland.

“So I think we’re in a very different place than we were 100 years ago, or 50 years ago, or even 20 years ago,” he said.

“The case for unification and the arguments for unification are a lot stronger than they were then, because of the things that have changed.”