Theresa May is set to become the UK’s next prime minister after Andrea Leadsom pulled out of the contest to become Conservative Party leader.
The timing of the handover of power from David Cameron is currently being discussed, but could be within days.
Mrs May, 59, who backed staying in the EU, has been home secretary since 2010.
Mrs Leadsom, who campaigned to leave the EU, said the UK needed “strong and stable government” and that Mrs May was “ideally placed” to implement Brexit.
In a speech earlier on Monday setting out her leadership campaign platform, Mrs May – who has rejected the argument that the next leader and prime minister had to have been someone on the winning side of the EU referendum – said: “Brexit means Brexit and we’re going to make a success of it.”
In her brief statement in Westminster, Mrs Leadsom said a nine-week leadership campaign at such a “critical time” for the UK would be “highly undesirable”.
A source close to the energy minister told BBC political editor Laura Kuenssberg “the abuse has been too great” for Mrs Leadsom during the contest.
Mrs Leadsom had apologised to Mrs May on Monday after suggesting in a weekend newspaper interview that being a mother made her a better candidate for the job.
Mrs Leadsom, who was flanked by some of her supporters, said: “Strong leadership is needed urgently to begin the work of withdrawing from the European Union. A nine-week leadership campaign at such a critical moment is highly undesirable.”
She said Mrs May, the home secretary, had the support of more than 60% of Conservative MPs and was “ideally placed to implement Brexit on the best possible terms for the British people and she has promised she will do so”.
Mrs Leadsom said she was “incredibly grateful” to the 84 colleagues who supported her leadership bid…
The leadership contest is being overseen by the 1922 committee of backbench Conservative MPs.
Its chairman, Graham Brady, said Mrs May would be formally confirmed as the new party leader as soon as the Conservative Party board had been consulted – saying there would be “no need to re-run the election”.
He declined to give an exact timetable for the next steps – other than to say it would not be “nine weeks” until Mr Cameron’s successor was in place.
The contest was originally scheduled to finish on 9 September.
The time between Gordon Brown winning the Labour leadership uncontested and succeeding Tony Blair as prime minister was 38 days.
Mrs Leadsom – who was a leading light of the Brexit campaign – made it in to the final two, alongside Mrs May – who campaigned for Remain – last week.
She secured the support of 84 MPs – including former Tory leader Iain Duncan Smith and Boris Johnson – compared with Mrs May’s 199 votes. Justice Secretary Michael Gove was eliminated after coming third.
There had originally been five contenders to succeed Mr Cameron, with MPs voting in two rounds to get that number down to two – with party’s 150,000-strong membership to have the final say.