Video report by ITV News Scotland Correspondent Peter Smith
In resigning as Scottish Conservatives leader Ruth Davidson has demanded the prime minister strike a Brexit deal with the European Union and urged MPs to back it.
The former journalist cited both "professional and personal" changes as reasons for stepping down, but did not shy away from the sticky issue of Brexit.
Following her resignation speech she told ITV News Scotland Correspondent Peter Smith her message to Boris Johnson was: "Prime minister, get us a deal in the European union."
And she said any MP against no deal should, "for God’s sake, get behind (a deal) and this time, at the fourth time of asking, vote for it."
Regarding the decision by Mr Johnson to prorogue Parliament, a spokesman for the Scottish Conservatives said her resignation was "not connected to today's Brexit developments in any way".
Her decision comes as the Queen approved Mr Johnson's request to suspend Parliament for five weeks.
In a resignation letter she wrote: “I have to be honest that where the idea of getting on the road to fight two elections in 20 months would once have fired me up, the threat of spending hundreds of hours away from my home and family now fills me with dread.
“That is no way to lead.”
She added in her letter she will continue to serve as a Member of Scottish Parliament (MSP) for Edinburgh Central until 2021.
Prime Minister Johnson paid tribute to Ms Davidson, saying: "On behalf of everyone in the Conservative and Unionist Party, I want to thank Ruth for her wonderful service over the last eight years.
"She has dedicated so much time and energy to the role and has been instrumental in the revival of our electoral fortunes in Scotland.
"She should take immeasurable pride in the pivotal role she played during the Scottish independence referendum campaign, where her passionate support for our Union was crucial to the result."
Former prime minister Theresa May said she was "sorry" to see Ms Davidson stepping down as leader.
She tweeted: "Thank you for all you've done for our party and our Union over the last eight years, and enjoy your well-deserved family time with Jen and Finn."
First Minister Nicola Sturgeon tweeted: "I wish Ruth well for the future. I know well the toll political leadership can take on family life, and no-one will grudge her more time with her young son.
"There will be opportunity later to discuss the politics of her decision - but for now, I'll simply send my best wishes."
Meanwhile, Scottish Liberal Democrat leader Willie Rennie said the Tories could struggle north of the border without Ms Davidson.
"There is little doubt that Ruth Davidson has brought a spark of life to the Conservatives and to Scottish, even UK politics, at a time that it really mattered," he said.
Ms Davidson described her eight-year tenure as leader - which included campaigning against leaving the union during the Scottish Independence Referendum - as the "privilege" of her life".
She added in her letter: "Inevitably, much has changed over the years of my leadership - both personally and in the wider political context.
"While I have not hidden the conflict I have felt over Brexit, I have attempted to chart a course for our party which recognises and respects the referendum result, while seeking to maximise opportunities and mitigate risks for key Scottish businesses and sectors."
"The biggest change, of course, has been starting a family. I cannot thank you, Jackson Carlaw and the wider party enough for the generosity and support you have all shown to Jen and me following the birth of baby Finn.
Watch Ruth Davidson's press conference in full
"It made my return to work in April as smooth as I could have hoped and I believe the flexibility shown by colleagues has allowed me these last months to continue operating successfully in my role as leader.
"However, as I look to the future, I see the Scottish Election due in 2021 and a credible threat from our opponents to force a general election before then.
"Having led our party through seven national elections and two referenda, I know the efforts, hours and travel required to fight such campaigns successfully."