Boris Johnson called U.K. Prime Minister Theresa May's Brexit proposal "deranged" and "entirely preposterous" in an interview with The Sunday Times — just days after he issued his own plan for "a better Brexit" with a lengthy piece in The Telegraph.

The big picture: Johnson's comments come at the start of the Conservative Party's annual conference as it finds itself in a civil war over how to move forward with Brexit. May wants to use the conference to unite her party behind her "soft" Brexit Chequers plan, which she repeatedly defended to the BBC in response to Johnson's comments as "the best deal for Britain," even though it's already been rejected as an option by the European Union.