Dominic Raab has resigned as the UK’s Brexit Secretary, citing the arrangements for Northern Ireland as his reason.

His decision comes after Britain and the EU agreed a draft proposal for the implementation of Brexit, which was welcomed by Ireland and the EU, but was criticised by both brexiteers in the UK and unionists in Northern Ireland.

In a letter to Prime Minister Theresa May, Raab explained that he resigned for two reasons: that the different arrangements for Northern Ireland threatened the integrity of the country; and the border backstop compromise, which he believes puts Britain in an unequal relationship with Europe.

I believe that the regulatory regime proposed for Northern Ireland presents a very real threat to the integrity of the United Kingdom.

Raab said: “I cannot support an indefinite backstop arrangement, where the EU would hold a veto over our ability to exit.

“The terms of the backstop amount to a hybrid of the EU Customs Union and Single Market obligations,” he added.

No democratic nation has ever signed up to be bound by such an extensive regime, imposed externally, without any democratic control over the laws to be applied, nor the ability to decide to exit the arrangement.

Raab’s decision will be considered a huge blow to May, who has now lost two Brexit Secretaries in the course of her negotiations with Europe.

His resignation underlines concerns that the proposed agreement will be shot down in the House of Commons.