Boris Johnson has won the United Kingdom's leadership election 92,153 votes to 46,656, becoming prime minister and leader of the ruling Conservative Party.

Johnson had been widely expected to win ever since Theresa May, the nation's outgoing prime minister, announced on May 24 that she was resigning following heavy criticism of her handling of the UK's exit from the European Union.

In a short but impassioned acceptance speech, Johnson thanked his leadership opponent Jeremy Hunt and May. He said that the party will "deliver Brexit, reunite the country and defeat" the leader of the opposition Labour Party Jeremy Corbyn.

"That's what we are going to do," Johnson said. "We know that we can do it, the people in our country know that we can do it, and I know that we will do it."

Johnson and Hunt were the last people standing in the leadership battle that had initially involved 10 hopefuls and was ultimately decided in a postal vote open to the party's 160,000 members.

Johnson takes over as party leader immediately and will be sworn in as prime minister on Wednesday.

He was an outspoken critic of May and says he will take the UK out of the EU on Oct 31, with or without a deal with the political bloc.

Following the result, May congratulated Johnson and said he will have her "full support from the back benches".

"Many congratulations to Boris Johnson on being elected leader of the Conservatives－we now need to work together to deliver a Brexit that works for the whole UK and to keep Jeremy Corbyn out of government," she wrote on Twitter.

Brexit Party leader Nigel Farage wrote on social media: "I wish Boris Johnson well as Prime Minister with his do or die pledge to deliver Brexit on Oct 31. Does he have the courage to deliver?"

Corbyn criticized Johnson's campaign platform and questioned the strength of his mandate.

"Boris Johnson has won the support of fewer than 100,000 unrepresentative Conservative Party members by promising tax cuts for the richest, presenting himself as the bankers' friend and pushing for a damaging 'no deal' Brexit. But he hasn't won the support of our country," Corbyn wrote on Twitter.

Before the result, UK Skills Minister Anne Milton resigned, saying she had "grave concerns" about Johnson's willingness to take the UK out of the EU without a deal. Alan Duncan resigned as Foreign Office minister on Monday, saying he refused to serve under Johnson, who he labeled a "circus act".

Further resignations are expected over the coming hours from both International Development Secretary Rory Stewart and Chancellor of the Exchequer Philip Hammond, who have both indicated they do not wish to serve in a Cabinet headed by Johnson.

Johnson entered politics as a member of Parliament in 2001, and later served two terms as Mayor of London. Johnson reentered Parliament in 2016, when he established himself as a leading figure in the "Vote Leave" campaign in the EU referendum.

Johnson was strongly tipped to take over as prime minister when the leave campaign won. However, his political ally Michael Gove dashed his chances by publicly questioning Johnson's ability to lead.

Theresa May then succeeded David Cameron as prime minister and appointed Johnson as foreign secretary. Johnson once again positioned himself as a potential leadership candidate when he resigned over May's handling of Brexit negotiations, paving the way for an ultimately successful run for the office of prime minister.

Donald Trump said on Twitter: "Congratulations to Boris Johnson on becoming the new Prime Minister of the United Kingdom. He will be great!"