On 9 January 2018, Johnson left his role as Minister for Universities and accepted a new position as Minister of Transport and Minister for London.
On 9 November 2018, Johnson resigned his position, citing disillusionment with the government's Brexit strategy and called for a fresh vote on Brexit with an option to remain. Johnson argued that Britain was "on the brink of the greatest crisis" since World War Two and claimed that what was on offer was not "anything like what was promised".
Johnson called on his Conservative Party MPs to vote down Theresa May's Brexit deal on 11 December 2018, stating that it was 'half baked' and the 'worst of both worlds'. Johnson resigned as a minister in December 2018 because he wanted to be free to endorse a proposed referendum on the Brexit withdrawal agreement.