Britain’s high military dependence on the US is “no longer tenable” and the UK has to become increasingly independent of the special relationship with Washington, a former Nato chief has said.

George Robertson, who last week accused British leaders of a “corrosive complacency” towards defence, said on Wednesday that the traditional allies were diverging over values – and that even after Donald Trump leaves the White House, the separation was likely to continue.

Lord Robertson, a former Labour defence minister and Nato secretary general, highlighted Trump’s unprovoked attack on Iran, his decision to levy tariffs on traditional allies and, “most jarringly”, he said, the threat to wrest Greenland from Denmark.

He said the diplomatic tone from the White House had “reached a historic low point” with Trump’s repeated public criticisms of the UK.