The prime minister made a slip of the tongue when she said on Wednesday there were several objectives for a “future customs union”.
That is a group of states agreeing to eliminate import taxes on trade between themselves and impose a common external tariff on imports from non-members.
Mrs May has ruled out Britain staying in any sort of customs union with the EU after Brexit.
While Labour has called for the UK to negotiate a new customs union deal with Brussels – such as those with Turkey, Andorra and San Marino.
The PM’s “war cabinet” is still in deadlock over two future customs relationships it is considering with the EU.
But during Prime Minister’s Questions, Mrs May said: “We want to ensure that we are able to continue to trade in as frictionless a way as possible.
“The suggestion that trade at the moment is entirely frictionless is actually not correct.
“We have set three very simple objectives for a future customs union.”
Her spokesman said minutes after the session finished: “She didn’t mean to say customs union, she meant customs arrangement.”
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UKIP seized on the slip, calling it an “absolute betrayal of the 17.4 million” – the number of people who voted for Brexit.
The party called it “BRINO” – an acronym for “Brexit in name only”.