DOWNING Street has tried to make things clearer over the weekend.

“It is not our policy to be in the customs union. It is not our policy to be in a customs union,” a source at No 10 told press on Sunday.

Yesterday. the Prime Minister’s official spokesman tried to clarify what that meant.

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“We are not joining a customs union or the customs union,” he said

Instead, he insisted the government is still deciding between two options it outlined last Autumn – a “highly streamlined customs arrangement”, which would attempt to follow what exists now, or a more ambitious “new customs partnership” with the EU.

Asked what the difference was between a customs union and a customs partnership, he replied to the journalists: “Err, I’m inclined to say ‘you tell me’ since you’re the ones who’ve been fascinating over [it].

“But the key point, as the Prime Minister has said on many many occasions, is that we need to have our own independent trade policy and be able to strike trade deals with the rest of the world.”

So, what is the difference between the customs union, a customs union, a customs arrangement and a customs partnership?

The customs union is the current EU system of which the UK is a part.

All EU member states, and Monaco, are part of a single trading area where all goods circulate freely, whether made in the EU or imported from outside.

So, if goods enter Ireland from the US, then duty is only paid in Ireland, rather than every country those goods go on to.

A customs union means a new trading bloc, where the UK would sign its own customs deal with the EU after leaving, allowing for some differences.

The EU already has similar arrangements in place, with Turkey, Andorra and San Marino.

What a customs arrangement is, is still a little fuzzy. It’s understood to mean a slightly looser deal to allow the UK have it’s own customs agreement with the EU and separate trade deals with non-EU nations.