Sinn Fein has warned that there could be "civil disobedience" if checkpoints appear after the UK leaves the European Union.

And Gerry Adams has urged the Taoiseach to block Brexit talks in December if the UK fails to guarantee that there will be no hard border.

Speaking at a Westminster Press conference yesterday, Sinn Fein MP Chris Hazzard warned that a hard border would cause anger and could lead to trouble.

The South Down MP said: "If we see a situation where we are going to have border customs posts or any particular type of hardware, I would think that would be something people won't want.

"And I go even further. An awful lot of the focus has been on maybe dissident republican organisations and threats, but it is wider than that - it goes right down to a feeling of civil disobedience.

"When you talk to normal people in civic society they are very, very angry and frustrated at even the thought of a customs post going up.

"So I think you will see widespread distaste for any notion of a hardened border, and I mean that from civic society. That's the strength of feeling from it."

TUV leader Jim Allister condemned the comments.

"We often hear vague suggestions that Brexit could lead to a return to violence," he said.

"It's always been clear that that threat didn't come from unionists. Now Hazzard has told us explicitly where that threat comes from.

"These comments should result in a renewed determination to ensure that the will of the British people is respected and a full and complete Brexit for the entire United Kingdom of Great Britain and Northern Ireland takes place.

"We cannot permit the threat of violence to blackmail us."

Ulster Unionist justice spokesman Doug Beattie said he was "absolutely staggered" by Mr Hazzard's "incendiary" remarks.

He added: "Not only have Sinn Fein abdicated their role in setting up a power-sharing Executive in Northern Ireland, we now have a Member of Parliament openly talking about a return to violence and civil disorder.

"There is nothing to be gained from whipping up fears or tensions, amongst either dissident republicans or career terrorists whose violent acts can do nothing to help stabilise the situation during these difficult times."

With a pre-Christmas election now averted, Taoiseach Leo Varadkar's focus will be firmly on crucial Brexit negotiations in Brussels on December 14 and 15.

Prime Minister Theresa May has rejected Mr Varadkar's demands for written commitments before trade talks begin to avoid checks on the border, even if it means Northern Ireland continues to apply EU trade rules while Britain diverges.

This has prompted Mr Varadkar to threaten to veto the start of trade talks at the summit.

Yesterday, Mr Adams said that Mr Varadkar must use the veto.

"Brexit in British Tory terms is bad for every single person on this island and bad for the economy. We need to be standing very firm. The North needs to be kept in the European Union," the outgoing Sinn Fein president said. He also described the DUP's position on the issue as "totally irrational and illogical", and accused it of being "disrespectful that the people of the North voted to remain and that should be upheld".

Referring to the collapse of power-sharing, he said even if the Executive was restored the differences between Sinn Fein and the DUP "will prevail".

"If we managed to get the institutions back in place there is a chasm between our position and the DUP position. The DUP ignores the consequences (of Brexit) for people, many of them unionist people," he added.

Meanwhile, the UK's Europe Minister Sir Alan Duncan has acknowledged that relations between the UK and Ireland were going through a "bumpy period".

Sir Alan suggested the current difficulties over the status of the border were partly as a result of Mr Varadkar's domestic political difficulties, which have resulted in the resignation of his deputy.

The Foreign Office minister told MPs he wanted a situation at the Northern Ireland border which would preserve "as much of the status quo" in people's everyday lives as possible.

Giving evidence to the Commons Foreign Affairs Committee, he said relations with Ireland were generally quite strong.

"There is a closeness of personal contacts which is pretty strong," he told MPs.

"It's a slightly bumpy period, born, I think, partly as well of their own domestic problems which we hope they will overcome."

Sir Alan described the relationship with Ireland as "enormously important" and the "preservation and continuation of the Northern Ireland peace process is absolutely essential".

He said the UK wanted a "frictionless border" so that as much as possible "of the status quo in people's daily life can continue unobstructed".

But Labour's former Europe Minister Chris Bryant said legal advice from the Foreign Office had suggested a hard border was inevitable if a country left the EU.

Belfast Telegraph