LONDON — British Prime Minister Liz Truss resigned Thursday after just six weeks in office, following a disastrous and rapidly reversed economic plan that sent the pound plunging and her government into chaos.

Having been formally appointed by Queen Elizabeth II on Sept. 6, Truss is now by far the shortest-serving prime minister in British history and will be remembered as one of the most calamitous.

The previous holder of this record, George Canning, lasted 119 days in the early 19th century; Truss will serve about 50.

A leadership contest to decide the next leader of the ruling Conservative Party, who will by default become the next prime minister, is now underway and will conclude in the next week.

The opposition Labour Party called for an immediate election.

What happens next after British Prime Minister Liz Truss’ resignation?

On Wednesday, Truss assured Parliament during the weekly Prime Minister’s Questions session that she was a “fighter, not a quitter.”

But leading a ruling party is only possible with respect and credibility. Truss increasingly had little of either, and quit just a day later.

“I recognize that given the situation I cannot deliver the mandate on which I was elected by the Conservative Party,” she said Thursday in a brief, unrepentant speech outside No. 10 Downing St.

“I have therefore spoken to his majesty the king to notify him that I am resigning as leader of the Conservative Party.”

She ended the statement by saying: “I will remain as prime minister until a successor is chosen.”

Attention is already turning to what happens next.

Rishi Sunak, Boris Johnson’s former finance minister who pointed out the folly of her economic plans, is the bookmakers’ favorite to replace her.

He came second to Truss in the race to succeed the scandal-hit Johnson.

There is also support in the party for experienced figure Penny Mordaunt, who earlier this week stood in for Truss in Parliament and assured lawmakers the prime minister was not hiding under a desk. There are even calls for Johnson to stage a dramatic return, just months after resigning under pressure from his own party and the public.

But with no clear successor waiting in the wings, there could be more uncertain days ahead.

NBC News