Liz Truss announced her resignation as Prime Minister of Great Britain outside Downing Street.
Her tenure lasted just 44 days, making her the UK's shortest-serving prime minister.
Speaking outside 10 Downing Street, she said she had come to realise that she "cannot deliver the mandate on which I was elected by the Conservative Party".
She said, reported The Telegraph: "I have therefore spoken to His Majesty The King to notify him that I am resigning as leader of the Conservative Party.
"This morning I met the chairman of the 1922 Committee Sir Graham Brady. We have agreed that there will be a leadership election to be completed within the next week.
"This will ensure that we remain on a path to deliver our fiscal plans and maintain our countries economic stability and national security. I will remain as Prime Minister until a successor has been chosen."
Meanwhile, the leader of the Labour party, Sir Keir Starmer, has called for an immediate general election.
In a statement following Liz Truss’s resignation, Starmer said:
The Conservative Party has shown it no longer has a mandate to govern.
After 12 years of Tory failure, the British people deserve so much better than this revolving door of chaos. In the last few years, the Tories have set record-high taxation, trashed our institutions and created a cost-of-living crisis. Now, they have crashed the economy so badly that people are facing £500 a month extra on their mortgages. The damage they have done will take years to fix.
Each one of these crises was made in Downing Street but paid for by the British public. Each one has left our country weaker and worse off.
The Tories cannot respond to their latest shambles by yet again simply clicking their fingers and shuffling the people at the top without the consent of the British people. They do not have a mandate to put the country through yet another experiment; Britain is not their personal fiefdom to run how they wish.
The British public deserve a proper say on the country’s future. They must have the chance to compare the Tories’ chaos with Labour’s plans to sort out their mess, grow the economy for working people and rebuild the country for a fairer, greener future. We must have a chance at a fresh start. We need a general election - now.
We don't need another Conservative Prime Minister lurching from crisis to crisis.
We need a General Election now and the Conservatives out of power.
— Ed Davey (@EdwardJDavey) October 20, 2022
Lib Dem leader, Sir Ed Davey, has also called for a general election.
At the same time, according to reports, Chancellor of the Exchequer Jeremy Hunt will not stand for the leadership contest.