There have been claims that the Foreign Secretary will no longer oversee MI6 following Mr Johnson’s appointment.

Writing in the Sunday Times, Adam Boulton said the Foreign and Commonwealth office is now left “with an unspecified role as it reels at the appointment of Boris Johnson as Foreign Secretary.”

The Government has strongly denied Mr Johnson will no longer be responsible for the Secret Service. A spokesperson told Politics.co.uk: "As has been long standing practice, responsibility for SIS and GCHQ lies with the Foreign Secretary. This has not changed and will not change."