The controversial chief aide plans to tour Britain’s most highly classified bases as he seeks to “radically shake up the military”, according to documents seen by an Australian newspaper.
“Plans for Britain's future defence and security should not be in the hands of a political adviser,” he warned.
And Layla Moran, the Liberal Democrat leadership candidate, said: “Britain's defence should not be the political plaything of Dominic Cummings. Boris Johnson needs to bench his adviser, for all our sakes.”
According to the documents, defence secretary Ben Wallace has forbidden officials from talking to Downing Street or Mr Cummings about the itinerary for his planned trip.
“The Secretary of State explicitly does not wish anyone to engage Number 10 or Dominic Cummings on this,” officials were told, the Herald reported.
“It is for the [the minister's special adviser] and the Secretary of State to engage in the first instance before delegating to officials.”
Meanwhile, a bitter internal struggle is underway about the UK’s future defence and security capabilities, with suggestions that No 10 will demand big cuts to military personnel.
But Mr Johnson’s political spokesman defended Mr Cummings’ tour, saying: “He is the prime minister’s senior adviser and so, as you would expect, he regularly visits government sites.
“Similar visits have taken place involving senior advisers under previous governments.”
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The tensions were laid bare when Nick Carter, the chief of the defence staff, appeared before the Commons defence committee on Tuesday.
Mark Francois, a hard Brexit-backing Tory MP warned him that Cummings “would sort out” the department in his “own way”, if it did not tackle its huge spending black holes.
Mr Cummings has previously been targeted by Labour over his security clearance opposition, after a whistleblower revealed the time he spent in Russia in his 20s.
Recent photographs – showing his security pass has a green band – suggest he has now been granted ‘developed vetting’ (DV) clearance, allowing him to view top-secret files without supervision.