THERESA May would seek a soft Brexit even if the Northern Irish border problem did not exist, her top aide has claimed.

No10 Chief of Staff Gavin Barwell shocked pro-Leave guests with the claim at a secret Downing Street meeting about the PM’s controversial White Paper on Thursday.

3 Theresa May did not view the Northern Ireland border as a decisive factor, even though others have painted it as so Credit: AP:Associated Press

3 The border between Ireland and Northern Ireland... marked by a sign riddled with bullet holes Credit: Getty Images - Getty

Former Remain campaigner Mr Barwell insisted it would make sense to stay closely tied to Brussels even if the UK did not have to in order to avoid a hard customs border with Ireland.

So far a major stumbling block to negotiations has been Northern Ireland, with the government pledging not to erect any barriers on the border with the republic.

The PM’s White Paper set out plans to stay closely aligned to Brussels for goods and standards, meaning a hard border will not be needed.

3 May's chief of staff Gavin Barwell Credit: Reuters

But Mr Barwell insisted there were were “economic arguments” beyond the border that meant the plan would make sense anyway.

However angry Tories see it as a compromise only required by the unique circumstances in Northern Ireland.

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A source at the meeting said: “Gavin told the briefing that even if the Northern Irish border was not an issue, because of the economic situation, there is an argument to be made that we should do this type of alignment anyway.”

“He said ‘It’s not just the Irish border but the economic arguments as well.”