Sinn Fein leader Mary Lou McDonald says the Irish government must prepare for a referendum on Irish unity given the uncertainty around Brexit.

Her comments came as protesters erected an eight-foot-high wall at one border crossing to demonstrate their opposition to any infrastructure there.

Ms McDonald told a Belfast conference there would be serious consequences for the island "if the Brexit fantasists have their way and there is a crash."

"No backstop means a hardening of the border, the undermining of the Good Friday Agreement, the loss of rights, continued uncertainty and instability," she explained.

"That is why the Irish government cannot, and must not, blink at this time.


Image: Sinn Fein leader Mary Lou McDonald says the Irish government must prepare for a referendum on Irish unity

"We say loudly and clearly that a hardening of the border is inconceivable and will be met by a demand for a unity referendum," she added.

The political theatre on the road between Newry in Northern Ireland and Dundalk in the Republic was staged by Border Communities Against Brexit.

Damian McGenity, one of the organisers, told Sky News that people fear a no-deal Brexit could turn the clock back.

Image: Protesters expressed their opposition to a hard border after Brexit

"The UK becomes a third country, there has to be inspections. How are they going to manage a 300-mile border?

"They're going to have to put this stuff on border roads," he added, pointing to the concrete wall behind him.

People dressed as customs officers and armed British soldiers, re-enacting a scene from the past by manning a fake checkpoint and camouflaged army watchtower.

One protester said: "I'll always have memories of sitting in the back of my Dad's car, being stopped at the border by 19-year-old British soldiers who didn't know how to hold a gun properly and ended up pointing it at your face."

Image: Protesters fear a no-deal Brexit could turn the clock back in Ireland

Another woman, accompanied by her two young children, added: "It was a very scary time to live and now I can see there's prosperity in the area.

"My children would be able to grow up here and have good jobs, good education and go across the border without any fear."

There is speculation that the UK parliament could accept an amendment to ditch the controversial backstop but protesters insisted the EU must not compromise.

They ended their demonstration by painting the words "no border here" on the wall, before demolishing it.