Boris Johnson tells Theresa May it is not Government's job to maintain 'no border' in Ireland, leaked memo reveals

Foreign Secretary appears to dismiss consequences of border posts – arguing '95 per cent plus of goods' would pass without checks regardless

Boris Johnson has told Theresa May it is not Britain’s responsibility to prevent a hard border in Ireland after Brexit, an explosive leaked memo has revealed.

The Foreign Secretary instead urged the Prime Minister to agree it should be the Government’s objective to prevent the crossing becoming “significantly harder”.

The memo, obtained by Sky News, also appears to dismiss the consequences of a hard border – arguing “95 per cent plus of goods” would pass without checks regardless.

The advice is certain to enrage the Irish Government, which has secured the EU’s backing that a return to border posts and checks must be avoided at all costs.

Furthermore, last year, Mr Johnson promised there would be no new hard border between the North and the Republic. During the Brexit referendum campaign, he said the border would be “absolutely unchanged”.

The leak also comes the day before the European Commission publishes a draft legal text setting out the commitment demanded from Britain to avoid a hard crossing.

It is expected to say Northern Ireland may need to be considered part of EU customs territory after Brexit, creating a single regulatory space on the island of Ireland with no internal barriers.

The arrangement would be the so-called “default” option conceded by Ms May in the December agreement between the EU and the UK.

However, hard Brexit supporters such as Mr Johnson fear that outcome would prevent Britain from breaking free from the EU’s economic structures, to pursue free trade deals elsewhere.

In December, under pressure from the Democratic Unionist Party, the Prime Minister agreed that continued “alignment” in Ireland would extend across the entire UK.

Ian Murray, a Labour MP and supporter of the pro-EU Open Britain campaign, accused Mr Johnson of being ready to “undermine the Good Friday Agreement”.

“It can be little wonder that negotiations over Ireland are now severely strained: because Theresa May and her ministers have consistently failed to be honest about the implications of the hard Brexit they seek,” Mr Murray said.

“As the threat to the integrity of the peace process from Brexit becomes clear, we all have the right to keep an open mind as to whether that it is too high a price to pay.”

In the memo seen by Sky News, Mr Johnson wrote: “It would be wrong to see the Government’s task as maintaining no border.”

He said the task should be to “stop the border becoming significantly harder”, adding that – even if that happened – “95 per cent plus of goods” could be expected to pass through without checks.

Opponents of a border are certain to warn that, even if only 5 per cent of goods were checked, it would still require a physical presence – and a potential target for terrorists.

Significantly, Sky News reported that the memo contained the phrase “not agreed technical advice” – suggesting Foreign Office officials had declined to endorse its contents.

Following the leak, Downing Street dismissed the prospect of returning to a hard border between northern and southern Ireland, saying it had made clear it was not an option "on numerous occasions".

Shadow Foreign Secretary Emily Thornberry told Sky News Mr Johnson was jeopardising peace in Ireland.

“I just don’t know where to start ... We need to have a soft border in Ireland in order to ensure that we have peace in Ireland. That is the truth and that's what Boris Johnson is supposed to be responsible for.

“The British Government have promised the people of northern and southern Ireland that there will be a soft border and now privately he’s saying that actually it probably will be a hard border, but hey, never mind.

“This is not acceptable. This is not grown-up politics, this is not responsible politics ... and it is simply telling lies to the British people."

Labour anti-Brexit MP David Lammy tweeted "God help us all this isn't just stupidity and ignorance but wilful recklessness",

Referring to the Leave campaign’s disputed claim Brexit would mean an extra £350m for the NHS, Ms Thornberry said: “It’s £350m on the side of a bus all over again. But this time, it's people's lives: 3,000 people died during the Troubles. This is not something to play around with."

The leak came on the day that Mr Johnson was attacked for comparing the complex challenge of the Irish border to managing the boundary between two London boroughs.

The Foreign Secretary said the UK would use technology, explaining how as London Mayor he electronically levied the congestion charge on vehicles crossing the boundary between Camden and Westminster.

Labour politicians slammed the comment as “stupidity” and suggested the Cabinet minister was living on a different planet.

A spokesman for Mr Johnson said the letter was "designed to outline how a highly facilitated border would work and help to make a successful Brexit".

"The letter points out there is a border now, and the task the (cabinet Brexit) committee face is stopping this becoming significantly harder," he said.

"It shows how we could manage a border without infrastructure or related checks and controls while protecting UK, Northern Ireland, Irish and EU interests."

He added: "We will not accept any physical infrastructure at the border, and will instead seek alternatives that allow us to leave the customs union and take back control of our money, borders, laws and trading policy."