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The Prime Minister spent last night trying to convince Cabinet members individually of her plans after her EU sherpa Olly Robbins concluded a technical-level agreement with his European Commission counterparts on Tuesday. After months of struggle to square the circle of the vexed Irish border issue, both sides have devised a working solution for the backstop, the insurance policy to prevent a hard border on the island of Ireland. But in a bid to please Northern Ireland’s Democratic Unionist Party and Brexiteer MPs, the Prime Minister may have signed up to the possibility of a permanent customs union with the EU, unless a better deal is reached within two years.

Last Friday, Michel Barnier’s deputy Sabine Weyand told EU27 ambassadors that a “customs union will be fully operational in the withdrawal agreement”, which only seeks to strengthen the possibility of it becoming the permanent solution moving forward. The EU’s deputy chief went further during the so-called ‘state of play’ briefing that the EU has succeeded in making the customs union “the basis of the future relationship”, according to an account of the meeting. She said: “We should be in the best negotiation position for the future relationship. “This requires the customs union as the basis of the future relationship.

Brexit news: Theresa May's deal could leave UK in permanent customs union with EU

“They must align their rules but the EU will retain all controls. They apply the same rules. “The UK wants a lot more from the future relationship, so EU retains its leverage.” Mrs May’s concession to Brussels also contains so-called “level playing field” agreements, which will lock Britain to EU rules for state aid and environmental and workers’ rights during the backstop, the EU official added. The new UK-wide customs arrangement backstop also means the UK “would have to sallow a link between access to products and fisheries in future agreements”.

The latest agreement virtually spells the end of the toxic Northern Ireland-specific backstop that Mrs May has been working to avoid after threats from the DUP to veto any agreement once it reaches the House of Commons. In her negotiation with Brussels, the Prime Minister ensured the EU’s original demands, which would have seen Northern Ireland essentially kept in the customs union and single market for goods, have been “buried” deep under the new UK-wide backstop, an EU official said. Northern Ireland provisions will likely pop up within the text and within annexes in the 500-page withdrawal agreement for scenarios where the UK-wide arrangement does not sufficiently prevent a hard border in Ireland. The backstop will, however, unlikely come into play until at least 2021 with a vital joint committee review to take place around July 2020.

Michel Barnier will brief EU27 ambassadors on the negotiations this afternoon