The Conservative Party source said Johnson had been surprised by the resignation of the party's chairman Oliver Dowden.

Asked if Johnson was worried about further resignations, the source said: "No, what makes you think that? He speaks to Rishi everyday ... he speaks to people every day about the day ahead and as you know there is a packed day ahead. He is seeing the prince (Charles) in a couple of hours, so no."

(Reporting by Andrew MacAskill; writing by Kate Holton; editing by Michael Holden)