Tory minister Lord Goldsmith has quit Rishi Sunak’s government over its “apathy” towards the environment – but comes after he was censured by the partygate probe.

The unelected Foreign Office minister has announced his resignation in a scathing letter to the Prime Minister Rishi Sunak, who he directly accuses of being “simply uninterested” in climate issues.

But the Prime Minister has accused Mr Goldsmith of apologising after refusing to apologise for a campaign to undermine an investigation into Boris Johnson.

Lord Goldsmith's role at the Foreign Office gave him responsibility for overseas territories, the Commonwealth, energy, climate and the environment.

The departure comes just a day after the peer was censured in a report by the Privileges Committee which named Mr Johnson allies said to have put “improper pressure” on its investigation into his Partygate lies to Parliament.

Read more: Boris Johnson allies criticised for trying to influence Partygte probe

In his letter, Lord Goldsmith wrote: “Prime Minister, having been able to get so much done previously, I have struggled even to hold the line in recent months.

“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.”

He added: “It has been a privilege to be able to work with so many talented people in government, in particular my private office, and 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 have faced makes continuing in my current role untenable."

In response, Mr Sunak said: “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.”

The SNP’s environment spokesperson, Patricia Gibson, said: “It’s an indictment of the UK Government’s lack of ambition and action in tackling the greatest crisis we face when their own environment minister resigns with such a condemnation of the Tories' record.

“Scotland can be a global leader in the fight against the climate crisis, but it’s increasingly clear that we need the full powers of independence to do so.”

The Liberal Democrats said the Prime Minister should have “had the guts” to sack Lord Goldsmith the day before his ministerial resignation following his “brutal” censure in a report by the Privileges Committee.

Read more: Climate advisers: UK has 'undermined' COP26 progress with oil push

Sarah Olney, the party’s Treasury spokeswoman, said: “This Conservative chaos is never-ending.

“Every day brings more resignations and scandal in this depressing Westminster soap opera.

“Rishi Sunak should have had the guts to sack Zac Goldsmith yesterday when he was brutally criticised by the partygate watchdog. Sunak is clearly too weak to control his own party.

“Zac Goldsmith’s resignation has at least confirmed what we have known all along, that Rishi Sunak’s Government doesn’t give a damn about the environment and animal rights.

“They have scrapped plans to stop puppy smuggling, watered down climate change action and let water companies pump sewage in our rivers. What a sorry state of affairs this is.”