The Irish government would impose checks on goods crossing the Northern Ireland border in the event of a no-deal Brexit, according to a leaked recording of the country’s deputy prime minister.

The opposition has seized on the admission, warning that there was now a “private understanding” in government that a hard border with the UK was increasingly likely.

Though the fact that a no-deal would create a hard border is well-established, the Irish government has up until this point said it would not impose one under any circumstances – but not spelled out how it could actually avoid one.

A border would be required under World Trade Organisation rules that both the UK and Ireland are subject to, and the countries could face external sanctions for not imposing one. Both say they want to avoid a border in order to comply with the Good Friday Agreement, however.

In a private conversation caught on tape Tánaiste Simon Coveney told a fellow minister there would be checks in the event of a no-deal “but we can't get into where they'll be at this stage”.

“But once you start talking about checks anywhere near the Border, people will start delving into that and all of a sudden we'll be the Government that reintroduced a physical border on the island of Ireland,” he said.

Micheál Martin, the leader of main opposition party Fianna Fáil, told the country’s parliament after the recording came to light that there was now “a private understanding” behind the scenes that border checks were increasingly likely.

“It seems there is a private understanding and knowledge of a border in the aftermath of a no-deal Brexit but at all costs that private understanding must not be shared with the public,” he said.

On Wednesday afternoon Irish prime minister Leo Varadkar denied his government has secret plans to impose a border.

“We are not planning for checks on the land border in Northern Ireland,” he said, adding that Mr Coveney had been misinterpreted.

“We had a hard border between Ireland and Northern Ireland. I remember it well during the Troubles and before the single market in 1993,” the Taoiseach said.

“I remember going there as a teenager. I remember the customs checks, I remember the 24-hour rule, I remember seeing soldiers, and I never want to see any of that ever again.”

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But pushed on how a border could actually be avoided, Mr Varadkar said the question was one for Brexiteers.