A poll on Irish unity should only be called after the “spade work” to decide the shape of the proposed state is complete, Sinn Fein’s president has said.

Mary Lou McDonald said it would take around two years to examine issues ranging from symbols and identity to how the health service and education system would work in a united Ireland.

Ahead of her party conference in Londonderry at the weekend, Ms McDonald expressed confidence that unification was within reach and reiterated her call for the Irish Government to convene a forum to discuss the issue.

The party Ard Fheis in Derry will see the unusual occurrence of a contested election for a senior leadership role, with former Stormont minister John O’Dowd hoping to replace Michelle O’Neill as vice president.

Ms McDonald rejected suggestions the party had moved to shut down public debate on the contest, or that Mr O’Dowd’s challenge was indicative of internal unease at her own leadership, after a series of disappointing elections south of the border.

John O’Dowd is hoping to replace Michelle O’Neill as vice president (Liam McBurney/PA)

On the issue of the timing of a potential border poll, Ms McDonald told the PA news agency: “What needs to happen firstly, is we need now for a forum, a citizens assembly, call it what you wish, to clear the space and to offer us the infrastructure, the architecture for a discussion on Irish unity amongst all of the stakeholders.

“And some of those issues will be around identity and symbols and so on. You know, they’re difficult issues, they’re important issues, but they’re not the only issues. It’s also around an Irish National Health Service.

“It’s around what does education provision look like. It’s also around investment and the huge economic dividends that I think can be brought about by Irish unity. And we need a space for that to happen.

“I think that the government in Dublin have a particular responsibility in this regard.

“I’ve said so to the Taoiseach (Leo Varadkar) on numerous occasions, and I think he and the government needs to convene that forum as a matter of absolute urgency.

“We need to talk about Ireland post-Brexit, we need to talk about the border, we need to talk about partition, we need to talk about the unity referendum.

“And we need to do the spade work because I think it’s entirely reasonable that people would say, ‘Well, what does this new Ireland look like in terms of human rights, civil rights, system of governance, but also in terms of bread and butter, people’s livelihoods and the prosperity of the island?’

“So that work needs to be done. If you go by the experience of other places like Scotland, for example, I think it took something like two years for them to do that kind of work.

“So I think you could use that type of a timeline for that work to be done. And thereafter, it’s a matter of calling the border poll.

“I’ve raised with Boris Johnson, as I have with Theresa May before him, the issue of the calling of that poll, and what they regard as the threshold that might trigger this, we’ve never had a satisfactory response.”

Ms McDonald said it was vital that unionist voices were heard in conversations about unification.

“It’s going to be a big challenge for us to ensure that we can have a debate that is fruitful, that’s respectful, that makes room for every perspective, including those for whom Irish unity is not their preferred outcome,” she said.

“And that’s OK, that’s going to be the unionist position. But even for that section of society, it’s important that they have their say on a whole wide range of issues because as and when Ireland is unified all of us have to be stakeholders and all of us have to have a sense of ownership of this new project, this new Irish state.”

After a low-key contest for the vice presidency, Ms McDonald denied that the party had been trying to stifle debate.

“No not at all, this an internal position, I mean the electorate is the Sinn Fein membership and the delegates at the Ard Fheis,” she said.

“Both Michelle and John have been talking to members across the country, to delegates and ultimately the delegates at the Ard Fheis make their decision.

“John has stepped forward, he’s more than entitled to, in fact any member of the party at any stage can contest for any of the positions.

“John’s a fine, talented and valued member of the leadership, Michelle obviously is my Leas Uachtarán (vice president).

“I have huge confidence in her, I work very closely with her and she will stand on her record and then the membership will decide.”

She said she did not agree with those suggesting it was a proxy challenge to her own record as leader.

“No I don’t, but I would also say that I am in this job because the membership put me in this job and because I enjoy their confidence, and that’s not something that you get sort of paranoid or, you know, skittish about – that’s how our system works.

“It’s entirely democratic. And we are all of us in the service of our party, of the membership and of, more importantly, the bigger political responsibilities that we have at this time.”