Boris Johnson's suggestion that a Libyan city could become the next Dubai once it had "cleared the dead bodies away" was "not appropriate", a spokesman for Theresa May has said.

Asked whether the foreign secretary would be sacked as a result of the comments, which prompted Tory MPs to demand his resignation, the Prime Minister's adviser said the matter is considered closed.

The rebuke follows a turbulent few days for Mrs May after Mr Johnson set out his own red lines on Brexit, prompting claims that he is planning to mount a leadership challenge.

The Foreign Secretary was condemned by Cabinet colleagues and Tory MPs over the remark, which he made last night on the fringes of the party's annual conference in Manchester.

Damian Green, the First Secretary of State, said Mr Johnson's remarks were unacceptable.