British Prime Minister Boris Johnson's former ethics adviser said on Thursday he had quit after being placed in an "odious" position over a plan that risked breaking the government's ministerial code.
Geidt, whose role was to advise Johnson on matters relating to the ministerial code of conduct, did not specify what the advice was about but said an intention to breach the code to suit a political end would have made a "mockery" of the rules.
Previously a top aide to Queen Elizabeth, Geidt was Johnson's second ethics adviser to quit in the last two years.
Media reports had suggested he previously considered resigning after Johnson was fined for attending a party during a Covid-19 national lockdown that he ordered.
"This request has placed me in an impossible and odious position," he said in his resignation letter to Johnson, which was published by the government on Thursday. "I can have no part in this."
Johnson said in a letter in response that the issue Geidt was asked to consider was a potential decision about trade tariffs linked to a body called the Trade Remedies Authority. He said the issue had previously had cross-party support but it may have conflicted with Britain's obligations under the World Trade Organization.
"My intention was to seek your advice on the national interest in protecting a crucial industry, which is protected in other European countries and would suffer material harm if we do not continue to apply such tariffs," Johnson wrote.
"In seeking your advice before any decision was taken, I was looking to ensure that we acted properly with due regard to the ministerial code."
British trade experts said the issue likely related to steel tariffs.
The previous holder of the ethics role resigned in 2020 in protest at Johnson's support for a minister who was found to have broken the code.
The government initially only published a brief statement from Geidt when it announced his resignation on Wednesday but came under pressure to reveal the reasons for his departure.
Johnson thanked Geidt for his work and said that his resignation came as a surprise because on Monday he had been told Geidt was happy to stay on until the end of the year.