The debate on Irish unity needs to be “deShinnerised”, a conference on the issue organised by Sinn Féin in Dublin has been told.

Kevin Maher, a writer and commentator, told the conference in Dublin that others besides Sinn Féin needed to begin to develop positions and raise their voices, otherwise the debate would remain marginalised.

“The debate needs to be deShinerised. The whole of Irish politics needs to buy into this debate,” said Mr Maher, a former special adviser to a Labour northern secretary Shaun Woodward.

He was one of the speakers at the conference, Towards a United Ireland, which is being held in the Mansion House in Dublin. Several hundred people are attending the conference, the aim of which is to broaden the debate to other voices, who have different views to Sinn Féin on the questions of unity and partition.

The conference was also the first in recent times where former deputy first minister Martin McGuinness was absent. His resignation on health grounds, and the speculation about his successor, dominated private conversations among those attending.

Opening the conference, party leader Gerry Adams read out a text from Mr McGuinness: “Sorry to miss the United Ireland conference. I will be there in spirit. I have struggled all my life for a United Ireland and I don’t intend to stop anytime soon.

“British rule in Ireland fails everyone in Ireland including our Unionists brothers and sisters. Onwards to the Republic.”

The person many people expect to be named as Mr McGuinness’ successor on Monday, the Tyrone MLA Michelle O’Neill, gave the keynote speech closing the event.

In the closing address, Ms O’Neill said the island would be better served by a single economy. Among the changes Sinn Féin wants she said was a dedicated Minister of State in the Irish Government with responsibility towards working for a United Ireland.

“Nobody has anything to fear from the republicans’ view of a united Ireland,” she said.

Asked afterwards about speculation about her impending elevation, Ms O’Neill declined to comment other than to say the decision would be made on Monday.

Another speaker, Mary Lou McDonald, is seen as the favourite to succeed Mr Adams when he stands down. The resignation of Mr McGuinness has renewed speculation about the timing of his decision to retire from his leadership position. Informed sources at the highest level said that only the Northern leadership issue will be dealt with on Monday and the question of the succession process for the South is for anther time.

In his address, Mr Adams said that he believed this generation could “conclude the unfinished business of 1916” but that it would need “political will and thoughtful strategies”.

He outlined how partition had set up two administrations, duplication of services, two sets of currencies, tax systems and laws.”

Mr Adams placed the notion of citizenship, of rights and equality and parity of esteem, at the centre of his argument.

“We cannot have the freedom of Ireland without the freedom of women.”

Turning to the impact of Breixt he said: “As the dire economic consequences of Brexit take shape there is an opportunity to look at new ways of governing ourselves here on the island.”

He criticised what he said was the lack of engagement from other political entities: “There is no strategic plan coming from our Government. That is a cause of real concern.

“That’s not just because of implications of hard border but also because of negative impact it will have on the Good Friday Agreement.”

The unionist commentator Alex Kane told the conference the notion of “deshinnerisation” was apposite. He said any such debate was not possible between Sinn Féin and the DUP.

“The two key main parties are not be able to exchange simple civic courtesies,” he said.

Mr Kane argued a border poll would be very divisive as 90 per cent of unionists would “under no circumstances be persuadable to a United Ireland.

“They don’t care, they do not want a united Ireland (under any circumstances),” he said.

He said that only 15 to 20 per cent of unionists would be persuadable. He also said that nobody was worse at making the argument for the union than unionists themselves. He said if such an argument could be made, a percentage of Catholics and nationalists could also be “persuadable” to the view that retaining the union was preferable.

Ms McDonald said the debate about a united Ireland was “not about grafting the six northern countries onto the south.

“What we are talking here is about building an entirely new entity,” she said.

That would necessitate imagination she added, where equality and citizenship were the core values, where religions were given esteem but not allowed to dominate, where equal esteem was given to the orange and green traditions.

“What we are looking for is a democracy not a theocracy,” she said.

In his speech, Mr Maher said that in Britain, Northern politics was pushed to the periphery and the British public and political class viewed it mostly with an air of indifference.

He focused on the economy as the keystone to the whole debate.

The party MEP Matt Carthy told the conference that it had been hard to get people interested in engaging with the issue of a united Ireland in the past two years, but that had changed with Brexit which had refocused minds in a dramatic way.