It is not the first time Mrs May and the Brexit guru have found themselves in disagreement over political appointments – even if indirectly.
In 2017, Mr Cummings wrote on Twitter that former Civil Service chief Jeremy Heywood was in a “parallel universe” on Brexit and warned Whitehall had “mega failed to prepare'” for the negotiations on the withdrawal agreement.
Moreover, Mr Cummings hit out at former Brexit Secretary David Davis, saying: “DD [David Davis] is manufactured exactly to specification as the perfect stooge for Heywood: thick as mince, lazy as a toad, and vain as Narcissus.”
The Brexit guru strongly believed Mr Davis was not the right person to lead the negotiations with the EU – particularly due to his lack of experience.
Mr Davis entered Westminster after a career in business.
He served in the Whips’ office for three years in the early Nineties and was ex-Prime Minister John Major’s Minister for Europe from 1994-1997 before returning to the front bench as Brexit Secretary in 2016.
JUST IN: Angela Merkel’s nuclear energy U-turn exposed