Andrea Leadsom said this morning she will be running for the Conservative leadership.
Leadsom, who campaigned for Brexit, tweeted this morning: "Let's make the most of the Brexit opportunities! #FreshStart"
|Brexit Britain: What you need to know|
Gove said: "I have come, reluctantly, to the conclusion that Boris cannot provide the leadership or build the team for the task ahead."
Boris Johnson was widely thought to want David Cameron's job, but said today he will not be taking part in the Conservative leadership race.
Theresa May, who kept a low profile during the EU referendum campaign, has said today that she will be running for the Tory top-job.
Work and pensions secretary Stephen Crabb declared his candidacy yesterday, as did Liam Fox.