Sir Keir Starmer has insisted he has "never authorised" attacks on his cabinet ministers, calling briefings against them "unacceptable".
The PM was speaking at Prime Minister's Questions the day after his allies told numerous media outlets he could face a leadership challenge from one of his colleagues, including Health Secretary Wes Streeting.
Conservative leader Kemi Badenoch accused the prime minister of running a "toxic" Downing Street and said it proved Sir Keir had "lost control of his government... and lost the trust of the British people".
Earlier, Streeting dismissed the claims of a challenge as "self-defeating nonsense" and said those behind the anonymous briefings should be sacked.