FORMER prime ministerial chief aide Dominic Cummings has said Vote Leave's vision post-Brexit meant "Ireland would have been a bit messy but so what".

He was director of Vote Leave, which successfully executed the 2016 referendum campaign for Britain's exit from the European Union.

After Boris Johnson succeeded Theresa May as British Prime Minister, Mr Cummings was appointed as his chief advisor.

In a social media exchange with Channel 4 journalist Krishnan Guru-Murthy and former Justice Secretary David Gauke, he insisted if his campaign group had handled the negotiations, customs checks would have been forced on the EU between the Republic and other member states.

"We'd have refused ANY checks anywhere and Ireland (would) not have dared build anything either," he claimed.

Mr Cummings said if the British government had done this Northern Ireland would "have been a minor part of the (negotiations)".

"We'd have made clear we'd have acted unilaterally if they d***** around babbling about GFA etc. Ireland became huge leverage for them cos of SW1 [slang for Westminster politicians and advisors] playing student politics, not realpolitik."

Mr Cummings predicted French president Emmanuel "Macron (would) threaten [to impose the custom checks] in this hypothetical scenario, given he threatened it in our actual world in 2019".

He added that it would "probably" not have come to this in reality, but when pressed by Mr Guru-Murthy about where the checks would have been he insisted Vote Leave architects would not have signed up to the controversial Northern Ireland Protocol.

"If (Vote Leave) had run things from 6/16 (June 2016) we'd have refused any checks in Irish Sea or to build anything on IRE land border.

"And we'd have pointed out GFA has f*** all to do with Brussels! IRE (would) have been a bit messy but so what. It's a small problem relative to others."

When author Sheila O'Flanagan described this "attitude to international law and treaties" as "shameful", Mr Cummings insisted it was about "priorities", which included stopping a second referendum, "binning Corbyn, science/tech".

"Compared to that, some problems in IRE are small. It was not US who drove the country into a culdesac 16-19! We were asked to sort it out..."

Mr Gauke said Mr Cumming's answers were "clear and illuminating", but described his approach as "reckless".