O'Neill: I hope Ireland will be reunified while I'm leader

But Mrs O’Neill, 40, rejected the suggestion her party’s desire to end partition meant it was not ideologically committed to making the powersharing institutions in Northern Ireland work.

“We do believe in the Assembly,” she insisted.

“The (1998) Good Friday Agreement was hard-fought for, it was the alternative to conflict, so we believe in the institutions that were set up under the Good Friday Agreement and we believe in making them work.

“Obviously we want a united Ireland and that’s not a secret, but we do want the institutions to work and no one has worked harder than Martin McGuinness to make that happen over the last 10 years.

“We believe an Assembly is best-placed to deliver for health, education right across all the departments in all of our public services.

“The Assembly was the only defence against Tory austerity, the worst impacts of welfare (reforms). I think the Assembly is absolutely necessary. Direct rule, unionist rule have all failed us in the past and will always fail us in the future. We do believe in the Assembly.”

In recent discussions on what a united Ireland might look like, Sinn Fein has suggested the potential of retaining a devolved regional Assembly at Stormont - one linked to the Dublin government, rather than Westminster.

“That’s the conversation we need to have,” said Mrs O’Neill.

“We have very much got an open mind in regard to shaping that future together.”

She also said Brexit had given fresh momentum to the debate around unity.

“Clearly, more and more people are questioning the national question now because of the implications of Brexit,” she said.

“It is going to be catastrophic for the island of Ireland. It is detrimental and undermines the Good Friday Agreement. So for those reasons, people are genuinely and urgently concerned about the implications.”

On the prospect of securing reunification while she led the party at Stormont, Mrs O’Neill said: “I would love to see that. That’s my job. Every day I try to bring that about, convince enough people that they would be better off in a united Ireland and that the Ireland that we envisage is one that will be an agreed Ireland, it will be one that we all can plan for together.”