British Home Secretary (interior minister) Amber Rudd said Sunday that Boris Johnson was not starting a leadership bid by setting out his plans for Brexit in a newspaper article, adding that his intervention was "absolutely fine."

A week before Prime Minister Theresa May sets out her vision for Brexit in a speech in the Italian city of Florence, Johnson, the foreign secretary, published a newspaper article that roamed well beyond his ministerial brief.

"I know what an irrepressible enthusiast (Johnson) is about Brexit, and what he's done is set it out there, I think it's absolutely fine, I would expect nothing less from Boris," Rudd said on the BBC's Andrew Marr show.

When asked if the article was a leadership challenge, Rudd said "No, I don't think it is."

"I think that he, like I, supports the prime minister at this difficult time as we try to conclude the negotiations with the EU," she said.