Sinn Fein president Mary Lou McDonald has called for the Irish Government to commit to holding a border poll if the United Kingdom crashes out of the European Union.

She said that the British Prime Minister Theresa May’s decision to delay the so-called “meaningful vote” in the House of Commons has caused “significant concern” across Ireland.

Ireland’s Foreign Affairs Minister Simon Coveney said the Government is stepping up its preparations for a no-deal Brexit and will be briefing the Cabinet about its contingency planning for a crash.

Ms McDonald called for ministers to share their ideas on preparing for a no-deal scenario.

“I would like to know the extent to which the Government is making preparations for constitutional transition and for the possibly of a referendum on unity because, if there is a crash, the damage arising from that will not be fleeting, it will be long term,” she said.

Speaking to the media on Tuesday, Ms McDonald said she has made Mrs May aware that, in the event of Britain crashing out of the EU, a referendum on Irish unity would “advance very quickly”.

“They couldn’t expect that, in a crash scenario, Ireland would endure so much damage and simply be prepared to soak that up. That would not be an acceptable position,” she added.

“I am due to have a call with Mrs May this (Tuesday) evening. I will reiterate our view and the vast view of the people in the north and south that the Withdrawal Agreement is only possible with the minimal protections within it intact. If she has any notion of diluting that down or negotiating back from that then she is very misguided.”

Taoiseach Leo Varadkar said he wanted to provide assurances which the UK may need without changing the fundamental substance of the draft withdrawal deal.

He added: “Demands for Irish unity and border polls I believe are disruptive and destructive to trying to achieve what we want to achieve, which is the ratification of this agreement.”

Ms McDonald accused hard-line Brexiteers of failing to accept that protections in the Withdrawal Agreement are necessary for Northern Ireland and the Republic.

“In the reality in the event of a crash there is only one way to protect Irish interests, and that is to remove the border. We cannot have a hard border or hardening of the border,” she continued.

“I want to know what is the state of preparedness of the Irish State to provide for a process of constitutional transition and a unity referendum which I believe will happen in any event. I believe that is the course we are on.

“In the event of a crash Brexit and no deal, it moves the timeline for all of that dramatically forward.

“The question for the Taoiseach (Leo Varadkar) and for all of Government is ‘Have you prepared for all of that? Are you ready for that?’

“This is a profound, political and social and economic crisis and challenge for us so the response has to be deeper than short-term measures.”