Junior minister Douglas Ross resigned from the British government on Tuesday over the handling of accusations that Prime Minister Boris Johnson's senior adviser had broken the coronavirus lockdown by travelling for help with childcare.
Dominic Cummings, Johnson's closest aide, refused to resign on Monday, saying he had done nothing wrong by driving 250 miles to northern England when Britain was under a strict lockdown.
Johnson's defence of Cummings, a key figure in his successful campaign to leave the European Union, has stirred anger in his Conservative Party, with some lawmakers calling for the aide to quit.
Ross, a junior minister in the Scotland Office, said in a letter he accepted Cummings' statement when he "clarified the actions he took in what he felt were the best interests of his family" but added: "However, these were decisions many others felt were not available to them".
"I have constituents who didn't get to say goodbye to loved ones, families who could not mourn together, people who didn't visit sick relatives because they followed the guidance of the government. I cannot in good faith tell them they were all wrong and one senior adviser to the government was right."
A Downing Street spokesman said: "The prime minister would like to thank Douglas Ross for his service to government and regrets his decision to stand down as Parliamentary Under Secretary of State for Scotland."
With a death toll of more than 47,000, Britain is Europe's worst-hit country and the government was already under pressure over its handling of the pandemic before newspaper allegations about Cummings were published on Friday.
A spokesman for Johnson repeated that the prime minister was "satisfied" with Cummings' explanation.
But his decision to travel during the lockdown has prompted fury among some in Britain, and several Conservative lawmakers demanded his dismissal after angry messages from voters.
A divisive figure, Cummings is seen by allies and enemies alike as Johnson's most important and influential strategist.
Giving him the chance to defend himself in front of the media in the Downing Street garden was a clear signal Johnson was not prepared to succumb to calls to sack the aide, instead doubling down that he had not done anything wrong.
But the row looked set to rumble on.
"To lose (Ross) from government is a disaster. His was one of clearest voices for the Union in government. It shows exactly why Cummings should be sacked," Adam Tomkins, a Conservative member of the Scottish Parliament, said.