The European Union has reassured the Government that no physical checks will be needed on the Border even if Britain crashes out of the union without a deal, Taoiseach Leo Varadkar has said.

Mr Varadkar said that such a “doomsday scenario” would mean that the “commitments of others” would have to be relied upon to prevent a hard border on the island of Ireland.

He indicated that this applies equally to the EU as it does to the UK.

Speaking after a special Cabinet meeting in Derrynane House, Co Kerry, the Taoiseach said the British government will be expected to honour its “cast iron guarantee” of the so-called backstop arrangement.

At the meeting, Ministers agreed to hire 700 additional customs officials to be deployed at ports and airports, and 300 extra staff to carry out checks on agricultural produce and animals travelling between Ireland and the UK after Brexit.

A Government statement said “significant” investment will also be needed to upgrade existing infrastructure at ports and airports, in particular Rosslare and Dublin Ports .

The Taoiseach said the Government is now stepping up its preparations for all Brexit eventualities.

As well as the UK promise on the backstop, the Taoiseach also noted that senior EU figures, such as Jean Claude Juncker, the president of the European Commission, have also promised the Government that no physical infrastructure will be required.

“Also President Juncker and my EU colleagues have on many occasions said that they wouldn’t require us to put in place a physical infrastructure and customs checks on the border between Northern Ireland and Ireland.”

Mr Varadkar also said he “profoundly” disagreed with comments made by former UK foreign secretary Boris Johnson, who yesterday said Northern Ireland issues have dominated the debate on Brexit.

“I am glad that Prime Minister May disagrees with him too,” Mr Varadkar said, noting Mrs May is visiting Northern Ireland this week. He also warned that the UK will be restricted in flying planes in European airspace in the event of a no deal Brexit.

“The situation at the moment is that the United Kingdom is part of the single European sky, and if they leave the EU they are not and that does mean that if there was a no deal hard Brexit next March the planes would not fly and Britain would be an island in many ways and that is something that they need to think about.

“You can not have your cake and eat it. You can’t take back your waters and then expect to use other people’s sky.”

“In the unlikely event that we have a hard Brexit next March, with no deal, I think every country will struggle to put in place the necessary infrastructure and customs and veterinary officials in their ports and airports. It won’t be just us.”

In such a scenario, the Taoiseach said, Irish measures that are planned to take two years, until the end of the post-Brexit transition phase, would have to be applied in a few months.

He repeated that a withdrawal treaty, including the backstop, must be agreed for the UK to be given a transition deal.