His relationship with then-UKIP party leader Nigel Farage was full of "animosity" and "tension"; on several occasions he called for Farage to step down as party leader. Farage called Carswell "irrelevant" in response to them supporting different campaigns to leave the European Union in the 2016 referendum. In response to Carswell calling for the party leader's resignation, Farage said that Carswell should "put up or shut up", further saying that "either he's going to have to accept that is unified or do something different". After Farage's resignation as UKIP leader following the EU referendum, Carswell tweeted a "sunshades smiley emoji", which some parts of the media described as showing the "uneasy relationship" between the two men, Carswell later said to the BBC that "I tweet smiley faces all the time, I'm very optimistic". He also said that while Farage had "played a role" in the referendum, the resignation was "a huge opportunity" for the party. This happened a week after Farage suggested that Carswell could be kicked out of the party, saying that "We find somebody inside our party who doesn't agree with anything the party stands for, it's a very odd state of affairs".