Liz Truss succeeded Boris Johnson as prime minister on 6 September after defeating Rishi Sunak in the Conservative Party leadership contest and meeting the Queen at Balmoral.
Liz Truss resigns as prime minister after just 44 days.
In a statement read outside Downing Street, Ms Truss said: “I came into office at a time of great economic and international instability.”
“Families and businesses were worried about how to pay their bills.”
Ms Truss added that she was elected “with a mandate to change this”, saying: “We delivered on energy bills.”
She says she recognises she “cannot deliver the mandate” on which she was elected and that there will be a leadership election “to be completed within the next week.”
Her time in office has been dominated by market chaos prompted by the mini-budget that was announced by former chancellor Kwasi Kwarteng last month.
Despite sacking Mr Kwarteen last week and reversing almost all the unfunded tax cuts that had been proposed, the prime minister’s position had continued to come under pressure.
The announcement, made by Truss outside Downing Street, follows the near-complete evaporation of her political authority which has seen her crash the markets, lose two key ministers and shed the confidence of almost all her own MPs.
Truss will be the shortest-serving prime minister in UK history.
New PM within the week.
Labour and Lib Dems call for immediate general election
The leader of the Labour party, Sir Keir Starmer, has called for an immediate general election.
Liz Truss’s resignation speech in full
I came into office at a time of great economic and international instability.
Families and businesses were worried about how to pay their bills.
Putin’s illegal war in Ukraine threatens the security of our whole continent.
And our country had been held back for too long by low economic growth.
I was elected by the Conservative Party with a mandate to change this.
We delivered on energy bills and on cutting national insurance.
And we set out a vision for a low tax, high growth economy – that would take advantage of the freedoms of Brexit.
I recognise though, given the situation, I cannot deliver the mandate on which I was elected by the Conservative Party.
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 Chair of the 1922 Committee Sir Graham Brady.
We have agreed there will be a leadership election to be completed in the next week.
This will ensure we remain on a path to deliver our fiscal plans and maintain our country’s economic stability and national security.
I will remain as Prime Minister until a successor has been chosen.