Boris Johnson says the public "don't give a monkey's" about the Downing Street leak row between him and Dominic Cummings.
It comes after his former chief adviser published a blistering 1,100-word blogpost, denying he was the so-called 'chatty rat' within Westminster.
Instead Mr Cummings claimed the Prime Minister tried to block an inquiry to find the person who leaked news of the second lockdown in November and the Mr Johnson's texts with Sir James Dyson.
He said the Prime Minister tried to prevent the probe to protect one of his fiancee Carrie Symonds' friends, however the Tory leader has denied this allegation.
When asked whether he thought his former adviser had leaked his texts with Mr Dyson, the Prime Minister told LBC: "I don't think people give a monkey's about this issue.
"What they care about is what we're doing to protect the health of the British public and that's what I care about."
Mr Cummings said the Cabinet Secretary had told the PM he was not behind the leaks and that all the evidence pointed to No 10 adviser Henry Newman and others in his office.
According to Mr Cummings, the Prime Minister had been "very upset" as it would cause him "very serious problems" with Miss Symonds if Mr Newman had to be fired and had asked whether the leak inquiry could be stopped.
A senior Government source said the allegation against Mr Newman, who is a close friend of Miss Symonds, was 'entirely false', according to the Daily Mail.
The Prime Minister also denied attempting to block the inquiry into the leaker, who shared messages between Mr Johnson and the head of Dyson.
In the texts, the Prime Minister promised to "fix" a tax issue for Sir James.
Mr Cummings also blasted his former boss's funding plans for the renovation of his official Downing Street flat.
He said his proposal to use money from Tory donors to pay for the work was 'unethical, foolish and possibly illegal'.
In his blogpost he claimed he told the Prime Minister that the move 'almost certainly broke the rules on proper disclosure of political donations'.
Downing Street announced yesterday that Mr Johnson had paid for the flat refurbishment himself.
In response to Mr Cummings' claims, a spokesman said: "At all times, the Government and ministers have acted in accordance with the appropriate codes of conduct and electoral law.
"Cabinet Office officials have been engaged and informed throughout and official advice has been followed."
A No 10 source accused Mr Cummings of being 'bitter about what happened since he's left' and 'engaged in systematic leaking' earlier this week.
The former Vote Leave boss hit back with his explosive blogpost last night.
He also claimed No 10's new director of communications Jack Doyle has made 'a number of false accusations' against him at the 'PM's request'.
Ministers are braced for further allegations when Mr Cummings appears next month before MPs investigating the Government's response to the coronavirus pandemic.
Downing Street said in a statement that ministers had acted at all times "in accordance with the appropriate codes of conduct and electoral law".
Labour said the Tories were fighting "like rats in a sack" demonstrating a "breath-taking contempt" for the public.
Labour deputy leader Angela Rayner said the Government was "lurching between cover-ups and cock-ups".
"Labour is focusing on jobs, crime and the NHS, while the Conservatives are fighting each other like rats in a sack and slipping deeper and deeper into the mire of sleaze," she said.
