The Sinn Féin President has warned the UK Prime Minister that it would be "unthinkable" to deny people the opportunity to vote on Irish unity if the UK crashes out of the EU without a deal.

Mary Lou McDonald was speaking after a meeting with Boris Johnson in Belfast this morning.

The new UK leader has continued to call for the Irish border backstop to be removed from the Brexit Withdrawal Agreement - and has used the threat of a no deal Brexit to try and force the EU back to the negotiating table.

It seems to me that Boris Johnson is quite complacent about Ireland being the collateral damage to Brexit - @MaryLouMcDonald pic.twitter.com/6aIxBOXUNj

— Sinn Féin (@sinnfeinireland) July 31, 2019

Deputy McDonald said he has "set the compass for a disorderly, crash Brexit" and has shown himself to be "quite complacent at the idea of Ireland being the collateral damage."

"We have challenged him very strongly on that policy," she said.

"We have set out very clearly that this would be catastrophic for the Irish economy, for Irish livelihoods, for our society, for our politics and for our peace accord."

We made it clear to Boris Johnson that a crash out Brexit would be catastrophic for our economy, our society and our peace agreements - @MaryLouMcDonald tells media at Stormont pic.twitter.com/7kGfLdgv5q

— Sinn Féin (@sinnfeinireland) July 31, 2019

The Sinn Féin leader said the "extensive planning" the UK has begun carrying out to prepare for a no deal scenario must include, "the Constitutional question and the issue of a border poll here in Ireland."

"We have stated to him very clearly that Brexit in any event, but certainly a disorderly Brexit, represents in anybody's language a dramatic change of circumstances on this island and that it would be unthinkable in those circumstances that people would not be given the opportunity to decide on our future together," she said.

"That is a conversation that we will continue with the Prime Minister."

Confidence and supply

Turning to the political impasse at Stormont, Deputy McDonald said the confidence and supply agreement between Mr Johnson's Conservative Party and the DUP had made the negotiations "very, very difficult."

She said the agreement was preventing the UK from acting with impartiality in the Northern political process.

"He tells us that he will act with absolute impartiality," she said. "We have told him that nobody believes that."

"Nobody believes that because there are no grounds to believe that there is any kind of impartiality much less strict impartiality.

"We have told him that the confidence and supply agreement between the Tories and the DUP poisoned the groundwater here politically and made it very, very, very difficult to sustain a negotiation - much less to land on a conclusion or an agreement.

Direct rule is unacceptable and would be a very dangerous act in turning the clock back - @MaryLouMcDonald tells media after meeting with British prime minister Boris Johnson pic.twitter.com/0c9MFzr2a4

— Sinn Féin (@sinnfeinireland) July 31, 2019

Border poll

She said the governments in London and Dublin need to begin preparing for a vote on Irish unity.

"He asked for our advice and we have strongly advised him that to make progress here, he needs to ensure that he is not the DUPs gopher," she said.

"He needs to stop mollycoddling them; he needs to spell out the realities of life to them and to put pressure on his unionist colleagues to ensure that we can land on an equitable and a sustainable agreement.

"We have advised him that constitutional change is in the air - he can't say that he hasn't been told.

"And the wise thing to do for London as Dublin is to appreciate the change is in the air and to start the preparation now."

She said that any expectation that people in the North would "take it on the chin" if he decided to " crash this part of Ireland out of the EU and cause the level of jeopardy and damage that would entail" was "deeply, deeply misguided."

Stormont talks

Mr Johnson is meeting with the all the main parties during his visit to the North - including a private dinner he held with his DUP colleagues last night.

Heading into meeting this morning, he said his "prime focus" was to do everything he can to restore a power-sharing government in Northern Ireland.

Asked whether the private dinner would lead to questions over his government's impartiality in the Stormont talks, he said: "It's all there in the Good Friday Agreement, we believe in complete impartiality and that's what we're going to observe."

The trip is the final leg of his tour of the UK, having spent Monday in Scotland and Tuesday in Wales.

He had been booed by protesters on his two trips so far.