Rishi Sunak has got into a public slanging match with Zac Goldsmith after he quit with a brutal attack on the government.
In an extraordinary resignation letter, the Tory peer accused the Prime Minister of being "simply uninterested" in environmental issues and damaging the country's reputation on the world stage.
But Mr Sunak hit back as he accused Lord Goldsmith of leaving government because he would not apologise for a tweet attacking the investigation into Boris Johnson's Partygate lies.
A damning report on Thursday named and shamed him as one of 10 Tories who had attempted to undermine the Privileges Committee's probe into the disgraced ex-PM.
The PM revealed he had told the minister to say sorry for suggesting the investigation into Mr Johnson was a "witch hunt".
"You were asked to apologise for your comments about the Privileges Committee as we felt they were incompatible with your position as a Minister of the Crown. You have decided to take a different course," he wrote in a reply to Lord Goldsmith's stinging resignation letter.
But in a fresh salvo, Lord Goldsmith accused the PM of "misleading" the public about his resignation.
In a statement posted on Twitter, he wrote: "I'd like to make clear I am happy to apologise for publicly sharing my views on the Privilege Committee.
"I firmly believe our Parliamentary democracy can only be strengthened by robust exchange and scrutiny and Parliamentarians should of course be free to be critical of its reports and proceedings. But as a Minister I shouldn't have commented publicly.
"No10 asked me to acknowledge that and made clear there was no question of my being sacked. I was - and am - happy to do so."
Lord Goldsmith doubled down on his criticism of Mr Sunak's premiership, adding: "I have tried hard in recent months to protect and build upon a strong UK record of international environmental leadership.
"That job has become significantly harder on his watch and I am saddened by the damage being done to our reputation globally as a result.
"When I compare what I and my amazing team in government were able to do before the current PM took office with the lethargy of today, I can no longer justify being in government."
Opposition parties had called for Lord Goldsmith to be sacked after he was highlighted as one of the Tories responsible for launching "vociferous attacks" on the investigation into Mr Johnson.
In a special report, the Privileges Committee pointed to a Twitter post from Lord Goldsmith where he retweeted someone describing its work as a "kangaroo court" and "witch hunt" against the former PM.
The peer had added: “Exactly this. There was only ever going to be one outcome and the evidence was totally irrelevant to it.”
Labour and the Liberal Democrats had demanded Mr Sunak remove him from his post as Minister of State for Overseas Territories but on Thursday Downing Street said he retained the PM's full confidence.
Lord Goldsmith blasted the government's broken promises on animal welfare and climate change in his resignation letter.
He wrote: "I have been horrified as bit by bit we have abandoned these commitments - domestically and on the world stage.
"More worrying the UK has visibly stepped off the world stage and withdrawn our leadership on climate and nature."
He continued: "The problem is not that the government is hostile to the environment, it is that you, our Prime Minister, are simply uninterested.
"That signal, or lack of it, has trickled down through Whitehall and caused a kind of paralysis."
Lord Goldsmith added: "It has been a privilege to have been able to make a difference to a cause I have been committed to for as long as I remember.
"But this government’s apathy in the face of the greatest challenge we face makes continuing in my role untenable. Reluctantly I am therefore stepping down."
At a Downing Street press conference, Mr Sunak dismissed the criticism.
The PM said: "I'm proud of the record of this government, and indeed of Zac's in government, making sure that we tackle climate change and protect our natural environment.
"The UK has played a leadership role globally and we will continue to do so."
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