The prime minister has sacked Zac Goldsmith as an environment minister and told him he will no longer be attending the cabinet.
The Conservative peer has been stripped of his brief overseeing animal welfare at Defra by Liz Truss, the new prime minister.
In a farewell letter to Defra staff, published on social media, Mr Goldsmith said he was 'very sad' to be leaving after a 'whirlwind' three years.
A close ally of former prime minister Boris Johnson, the peer listed his achievements, including in forestry, plastic pollution and the oceans.
“We have so much more to do to turn the tide here. The UK is, after all, one of the world’s most nature-depleted countries," he said.
"But if Defra continues to get the backing you need and deserve across government, you can and you will turn the tide.”
It comes after Ranil Jayawardena was appointed the new Defra Secretary earlier this month following a reshuffle PM Truss.
Responding to his new role, Mr Jayawardena said it was a 'privilege' to be appointed the Secretary of State for Defra.
"From food security and backing British farmers, to water security and growing our rural economy, I know that there is much to do," he said, adding that it was also important to recognise where food came from.
"I recently met local farmers with the NFU, to discuss the government’s support for British farming and the export growth ahead."
Meanwhile, former Chief Whip Mark Spencer was appointed Defra Minister of State, replacing Victoria Prentis who was in the role for over two years.