The Sinn Féin leader Mary Lou McDonald has said plans for a vote on Irish unity need to be stepped up, as the debate is already taking place.

She has said the British Prime Minister Theresa May has acted "in bad faith" by reneging on her Brexit deal.

Her comments came ahead of a Sinn Féin Irish unity event, which took place place in Dublin, along with deputy party leader Michelle O'Neill.

The party has said it was a meeting to discuss a pathway to a united Ireland.

Ms O'Neill said momentum towards a united Ireland must be built upon.

"Over the space of the last number of years, politics on the island of Ireland has changed utterly.

"Sinn Féin has been at the centre of this public and political discourse. We are a national independence movement.

"We have to build a mass movement and momentum for Irish unity, both here in Ireland and internationally.

"We must campaign - bringing others onside - for a referendum, secure a referendum and then win it.

"This requires credible political strategies, which the people want to support, and a strong Sinn Féin party, so we deliver real change.

"We must get out front and sell our credible vision and the merits and benefits of reunification against the cost of partition, division and remaining within the union.

"We cannot sit back and assume the conditions previously outlined will hand us unity on a plate."

'Essentially rejected the withdrawal agreement'

Ms McDonald has said Britain has put Irish protections "through the shredder".

"Theresa May has acted in absolutely bad faith, the British government have reneged on an agreement that was freely entered into.

"They have put the backstop, which is the basic protections for Ireland, through the shredder.

"And we are simply saying that the Good Friday Agreement contains a provision for the people democratically to decide and adjudicate on the border - and to take the opportunity to remove it if it's a thing that the border can't be mitigated, if it is a thing that we cannot avoid a hard border, and everything that would flow from that on our island... the Good Friday Agreement provides for the people to have their say.

"And I think it's so important now that the Irish Government convenes a forum on Irish unity, that we begin the planning for the time ahead.

"There's no point in the Government burying its head in the sand and in a very flat-footed way walking Ireland into chaos and disorganisation".

UK PM Theresa May address the House of Commons in London | File photo

Ms McDonald said the Government planning for every Brexit outcome should include planning for a vote on a united Ireland.

"The Tories and Mrs May have made clear that they have now essentially rejected the withdrawal agreement, they have rejected the protocol and the backstop to protest Irish interests."

She added that the Tories are "acting recklessly and clearly in a very hostile manner to Irish interests".

"I would say that the debate on Irish unity is underway, I would say that the polls North and South reflect the fact that the people do not want a hard border on their island - that their if a crash by the British Tories people want Irish unity.

"I would say to the Government that we're on that path anyway, so plan."

"It's very clear to me that we are now in a period of very great danger and jeopardy for our entire island - and it's very clear to me that we need to plan and be prepared for every eventuality.

"The Good Friday Agreement provides for a referendum on Irish unity: the Government shouldn't be afraid of that, the Government should regard that as an opportunity".