It comes after British Justice Secretary Michael Gove criticised him
Former London Mayor Boris Johnson has announced he will not be standing in the Conservative leadership contest in Britain.
It comes after British Justice Secretary Michael Gove joined the race to be the next Tory leader, saying he did not believe Mr Johnson could "provide the leadership" for the task ahead.
Mr Gove repeatedly said he had no leadership ambitions, but he dropped the bombshell just hours before the nominations deadline on Thursday.
The declaration was seen as a blow for Mr Johnson, who was expected to stand with the backing of Mr Gove.
The pair campaigned side by side during the EU referendum campaign to secure the shock Brexit victory.
But Mr Gove said events since last week had "weighed heavily with me" and led him to change his mind.
"I respect and admire all the candidates running for the leadership. In particular, I wanted to help build a team behind Boris Johnson so that a politician who argued for leaving the European Union could lead us to a better future," he said in a statement.
"But I have come, reluctantly, to the conclusion that Boris cannot provide the leadership or build the team for the task ahead."
"I have, therefore, decided to put my name forward for the leadership."
"I want there to be an open and positive debate about the path the country will now take. Whatever the verdict of that debate I will respect it."
"In the next few days I will lay out my plan for the United Kingdom which I hope can provide unity and change."
While British Home Secretary Theresa May - who was deemed by many to be Mr Johnson's main rival in the race - pledged to unite both the Conservative Party and the country.
"We need a bold new positive vision for our country...the country needs strong leadership and a clear sense of direction," she said.
Mrs May backed Remain - but did so in a less provocative way than many of her senior Tory colleagues and was careful not to alienate either side.
In a move to garner the support of the eurosceptics in her party, she asserted: "Brexit means Brexit...there must be no attempts to remain inside the EU, no attempts to rejoin it through the back door and no second referendum."
"The country voted to leave the European Union and it is the duty of the Government and Parliament to make sure we do just that."
She said there should be no general election until 2020 and no "Brexit budget", adding Article 50 - which sets into motion the two-year window for leaving the EU - should not be triggered before the end of this year.