Boris Johnson has “strong views on Brexit … but so do I”, Theresa May has insisted, after resisting calls for the sacking of the foreign secretary in the wake of an explosive leaked recording.

In a private speech to the Conservative Way Forward group, Boris Johnson is heard dismissing the cautious approach of Philip Hammond’s Treasury, which he said had focused on “mumbo jumbo” predictions about short-term disruption, instead of the potential gains from leaving the EU.  Johnson also portrayed the Treasury as “the heart of remain”.

May, who was in the air en route to the G7 summit in Canada when the foreign secretary’s words were leaked, was questioned about Johnson’s comments upon landing in Quebec.

In an interview with Channel 4 News , Theresa May said: "These are complex negotiations. Boris has strong views on Brexit but so do I.  I want to deliver for the British people, that’s exactly what we are doing as a government and if you look at the process of these negotiations – nobody ever said it was going to be easy."

Philip Hammond hit back at Boris Johnson on Friday, saying he favoured a collaborative rather than confrontational approach. “My experience has been that ... a collaborative approach ... is generally more productive than a confrontational approach,” he said, noting that his advice to his colleagues would be to engage with Britain’s European partners if they wanted a good Brexit deal.

Earlier, Scotland’s first minister, Nicola Sturgeon, also called for Johnson to go. In an interview with  BBC, Sturgeon said: “Any prime minister that had any semblance of authority would have got rid of Boris Johnson a long time ago, not just because of comments like this ... I just don’t think Boris Johnson is somebody who should be in one of the high offices of state.”