Theresa May is “distinctly unimpressed” by the turf war that has erupted between Liam Fox and Boris Johnson over control of the Foreign Office, according to No 10 sources, in what constitutes the first major row in her government.

Tensions within the administration were revealed by a leaked letter in which Dr Fox, the international trade secretary, launched a power offensive on Mr Johnson’s department. Mrs May let it be known that she strongly disapproves of such behaviour and Downing Street insiders stressed last night that she believes “there is a big job to do and people need to get on with it”.

Dr Fox sent the foreign secretary a missive last month, which was copied to Mrs May, proposing a “rational restructuring” that would