Brexit is a symptom of a Britain that has “struggled” to accept it is “not as important in the world” as it once was, Ireland’s prime minister has said.

In an interview on Irish radio on Friday, Leo Varadkar said the UK faced decades of economic decline as a result of its decision to pull out of the European Union.

He also warned that the incoming prime minister in the UK would face a “serious reality check” about Brexit when they took office – with both candidates for Tory leadership currently “in campaign mode” and ignoring the evidence.

“A consequence of Brexit for Britain is that it will fall into relative economic decline for many decades, probably be overtaken by France again and slowly over time it’ll be overtaken by lots of countries in Asia,” Mr Varadkar told the Newstalk radio station.

“One of the difficulties for Britain is they’re struggling to cope with the fact that as a country and an economy they’re not as important in the world as they used to be. There are 100 million people living in Vietnam, they’re going to be overtaken by Korea, India economically.”

The Taoiseach said most European countries understood the “inevitable” transition and that they needed to “stick together and integrate so we can preserve our way of life, our prosperity, our peace and security”.

“Britain has never really fully accepted that in the way that France and Germany and Italy did after the war,” he continued.

In the same interview on Friday, Mr Varadkar suggested the Irish government was exploring the idea of checks at Irish sea ports in the event of a no-deal Brexit.

“The kind of things that we’re looking at and proposing, for example, is that the entire island of Ireland will be treated the same when it comes to agriculture or food, and that any SPS [sanitary and phytosanitary] checks would happen at the ports,” he told the broadcaster.

Stephen Barclay, Brexit secretary, said Ireland would suffer from no deal (EPA)

“That would mean Britain accepting that Northern Ireland is being treated differently. The other things obviously are checks at business level, and random checks and controls, and we’ll have to have a lot more of them anyway because of smuggling.”

Speaking earlier this week, Stephen Barclay, the secretary of state for exiting the European Union, said a no-deal Brexit would do more damage to Ireland than to the UK because 40 per cent of Irish trade travels through the straits of Dover – where there would be serious disruption.

Opposing protesters flock to parliament on would be date of Brexit Show all 30 1 /30 Opposing protesters flock to parliament on would be date of Brexit Opposing protesters flock to parliament on would be date of Brexit Pro-Brexit leave the European Union supporters attend a rally in Parliament Square after the final leg of the "March to Leave" in London AP Opposing protesters flock to parliament on would be date of Brexit The protest march which started on March 16 in Sunderland, north east England, finished on what was the original date for Brexit to happen before the recent extension Reuters Opposing protesters flock to parliament on would be date of Brexit A Brexit supporter holds up a poster during a rally after the final leg of the "March to Leave" in London, Friday, March 29, 2019. Pro-Brexit demonstrators were gathering in central London on the day that Britain was originally scheduled to leave the European Union. (AP Photo/ Kirsty Wigglesworth) Kirsty Wigglesworth AP Opposing protesters flock to parliament on would be date of Brexit A pro-Brexit protester holds a sign next to a statue of Winston Churchill at the March to Leave demonstration in London, Britain March 29, 2019. REUTERS/Toby Melville TOBY MELVILLE Reuters Opposing protesters flock to parliament on would be date of Brexit Brexit demonstrators in Parliament Square in Westminster, London. PRESS ASSOCIATION Photo. Picture date: Friday March 29, 2019. See PA story POLITICS Brexit. Photo credit should read: Jonathan Brady/PA Wire Jonathan Brady PA Opposing protesters flock to parliament on would be date of Brexit Pro-Brexit protesters hold signs and wave flags at the March to Leave demonstration in London, Britain March 29, 2019. 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