In the 2016 UK referendum on EU membership, she voted for the UK to leave the EU. On 28 June, she accidentally sent a private email meant to be read by Gove and his close advisors to a member of the public, who leaked it to the press. In the email, Vine had advised her husband not to back Boris Johnson's bid to become leader of the Conservative Party unless 'specific assurances' were given to him. Two days later, Johnson unexpectedly dropped out of the 2016 Conservative Party leadership election, after Gove made a surprise bid to become leader.