Her remark will be seen as a slapdown for the Foreign Secretary, who was accused by Home Secretary Amber Rudd of trying to act as a “backseat driver” by releasing his 4,000-word essay days before the PM delivers a crucial speech on Brexit in Italy.
In her first public comment on Mr Johnson’s intervention, Mrs May insisted that the Government was united behind the principles she set out at Lancaster House earlier this year, when she said Britain was leaving the European single market and customs union and seeking a new “deep and special partnership” with the EU.
Asked whether she was frustrated by the Foreign Secretary’s actions, Mrs May told reporters travelling with her on a visit to Canada: “Boris is Boris. I’m clear that what the Government is doing and what the Cabinet is doing is that we... base our negotiations on the principles set out at Lancaster House.”
She insisted: “This Government is driven from the front and we are all going to the same destination, because we are all agreed on the basis of the Lancaster House speech.
“We are all agreed as a Government about the importance of ensuring the right deal for Britain, the right withdrawal agreement but also the right deal on a special partnership between the EU and UK for the future.
“We are all optimistic about what we can be achieving for the UK for the future.”