The deputy leader of the SNP, Stewart Hosie, will stand down from his position after the party was rocked by headlines about his affair with a political journalist.
Last Monday, the Scottish Daily Mail revealed both Hosie and fellow SNP MP Angus MacNeil had separated from their wives after affairs with journalist Serena Cowdy. Hosie's wife, Shona Robison, is the Scottish government's health secretary and a close friend of party leader Nicola Sturgeon.
In a letter to Sturgeon, Hosie has apologised for "any hurt and upset" he has caused and said that this week's headlines have exacerbated his high blood pressure. He will stand down at the party's autumn conference to concentrate on his health and his constituency work.
"I am writing to you firstly to apologise for any hurt and upset I have caused to friends, family and colleagues," wrote Hosie. "That was never my intention."
"I am also writing to tell you of my intention not to seek re-election as depute leader of the SNP at this year's annual conference, giving ample time for the party to choose a successor.
"As you know I have been admitted to hospital on three occasions in the past few years with very high blood pressure. In that regard, the stress of the intense scrutiny of my private life has been very difficult."
Hosie added: "I intend to concentrate on my constituents, my responsibilities at Westminster, and most importantly, my health. It has been a pleasure to serve under your leadership and I hope to do so for many years to come."
In her reply, Sturgeon said the outgoing deputy leader can be "very proud" of his time in the role, adding: "I know you will continue to make a valuable contribution to the party in many ways and, in particular, through your work in your constituency and as part of the Westminster group."
There were reports last month that Hosie was due to lead a fresh SNP drive for independence this summer, but an SNP source told BuzzFeed News that, following Sunday's announcement, they expect him to have "a lesser role" in the campaign.
The deadline for deputy leader nominations will be 5 August, and the results of the election will be announced at September's conference.