Work and Pensions Secretary Esther McVey has resigned. She follows Brexit secretary Dominic Raab and Shailesh Vara as Northern Ireland Minister.
It's after Theresa's May's Brexit plan was approved by Cabinet last night.
Today, I have resigned as Brexit Secretary. I cannot in good conscience support the terms proposed for our deal with the EU. Here is my letter to the PM explaining my reasons, and my enduring respect for her. pic.twitter.com/tf5CUZnnUz
— Dominic Raab (@DominicRaab) November 15, 2018
May now faces a battle to push it through Parliament with the Labour party announcing they won't back the plan.
Speaking in the House of Commons this morning, Therea May insists she's taken "the right choices, not the easy ones" on Brexit.
The British PM admitted it has not been a comfortable process and told the house that withdrawing after 40 years was always going to be complex.
Mrs May told members of Parliament "We can choose to leave with no deal or we can risk no Brexit at all. Or we can choose to unite, and support the best deal that can be negotiated."
Meanwhile, the EU's Chief Brexit Negotiator warns there is a long road ahead before Brexit is finalised.
Michel Barnier says the deal is fair and balanced and ensures no hard border on the island of Ireland.
EU leaders will now gather for an emergency summit to sign off the draft Brexit agreement on Sunday 25 November.
The Taoiseach and EU leaders welcomed the deal, but the British Prime Minister faces a massive battle to get it passed in Parliament.
The 585 page withdrawal agreement was published yesterday and sets out how the UK will divorce the EU.
Key from an Irish point of view is the agreement on the backstop - the insurance policy to avoid a hard border on the island.
It's what comes into place if there is no trade deal reached between the EU and UK - and won't budge until there's an agreement.
It would see all of the UK in a single customs union, where trade rules and standards are kept so similar to the EU's that border checks won't be needed.
It's a significant win for the government, who got pretty much exactly what they wanted.
But the deal has several parts that may be unpalatable for unionists - Northern Ireland will be more closely tied to the EU than the rest of the UK.
And some goods coming from mainland Britain into Northern Ireland will be subject to checks as a result.
It's a massive uphill battle for Theresa May to now get this across the line in her parliament.
Many MPs are completely against it, and she may face a vote of no confidence from Tory rebels today.
But she's insisted this is the best deal for the UK - and European leaders have hailed it as a big step forward.
May now enters the trenches again to build political support for the deal.
Reporting by Sean Defoe.