What is the customs backstop?

Analysis: Political correspondent Benjamin Kentish outlines the measure that has parliament deadlocked and why it's so controversial

(AP)

It was the cause of months of deadlock between the UK and the EU, and is the basis of so much anger from Tory MPs that it threatens to split the Conservatives and topple Theresa May's government. But what is the customs backstop part of the Brexit agreement and why is it so controversial?

In short, the backstop is an insurance policy. It spells out what will happen if the UK and EU cannot agree a trade deal which maintains an open border between Northern Ireland and the Republic of Ireland.

The EU insisted on the fall-back, in part at the request of the Irish government, because an open border is a key part of the 1998 Good Friday Agreement that brought peace to the island of Ireland.

The UK and the EU both say they do not want the backstop to be implemented but it is the default option until a deal on the future relationship is agreed.

The backstop would see the whole of the UK enter into a customs union with the EU, while Northern Ireland would also have to abide by EU single market rules on goods.

This would remove the need for checks on goods travelling between Northern Ireland and Ireland, because the two territories would fall under the same tariffs and the same regulations.

However, Northern Ireland would remain in part of the EU single market, while the rest of the UK would not.

That would mean there would have to be new regulatory checks on goods travelling between Northern Ireland and the rest of the UK, because they would fall under different regulatory regimes. The EU would need to be sure that goods from Great Britain entering the EU via the Northern Irish border met European standards.

The need for these new checks is a major problem for the Democratic Unionist Party (DUP), which props up Ms May's government but is staunchly opposed to the backstop and, as a result, the proposed Brexit deal as a whole.

Unionists fear that a policy which would see Northern Ireland and Great Britain fall under different regulations, but Northern Ireland and Ireland come under the same regime, could be the first step towards the break-up of the United Kingdom and the unification of Ireland.

While many Tory MPs also strongly oppose the backstop, they mostly do so for different reasons to the DUP.

Brexiteers fear that the UK would not be able to exit the backstop without the EU’s approval, because the draft withdrawal agreement says the EU and the UK must “decide jointly” if and when the mechanism is no longer necessary.

Eurosceptics are also concerned that the backstop is “indefinite”, because the withdrawal agreement includes no time limit. They fear it could see the UK trapped in a customs union with the EU permanently - restricting, they say, the UK's ability to negotiate trade deals with other countries.

Delaying the parliamentary vote on her Brexit deal, Ms May promised to secure fresh assurances from the EU on the temporary nature of the backstop and the UK's ability to exit it. But with Brussels insisting that the withdrawal agreement cannot be re-negotiated, the row over the policy looks set to rumble on.

The backstop could well scupper Ms May's Brexit plan and, some pro-Europeans hope, make a second referendum all but inevitable.

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