Ruth Davidson quit as leader of the Conservative Party in Scotland on Thursday, saying she could no longer juggle the demands of being a politician with family life and suggesting she would no longer stand as a politician in 2021.

The 40-year-old led a resurgence of the Conservatives in Scotland during her eight years in charge, providing a counterweight to Nicola Sturgeon's Scottish National Party and winning key seats to help the party retain power in Westminster.

Davidson, who had backed Remain in the 2016 European Union referendum, said she would continue to support the party, the prime minister and Scotland's place in the United Kingdom.

"I fear that having tried to be a good leader over the years, I have proved a poor daughter, sister, partner and friend," she said in a letter to the chairman of the Scottish party.