Conservative MSP Graham Simpson has defected to Reform.
Simpson announced his move as he appeared at a press conference in Scotland with Reform leader Nigel Farage.
Simpson told journalists that many would not be surprised to see him defect, and that leaving the Conservatives was "an enormous wrench".
He is the second MSP to leave the partys Holyrood group in the past week.
Simpson becomes Reforms sole current MSP.
Michelle Ballantyne sat as a Reform member at the Scottish Parliament from January to May 2021, having left the Conservatives the previous year and sitting for a short spell as an independent.
She lost her seat at the May 2021 election.
Simpson has been an MSP for the Central Scotland region since 2016. He is a former journalist with The Sun and Daily Record.
Speaking at a press conference in Broxburn, West Lothian, he said: "Its fair to say that some of you wont be surprised to see me here, given that the Scottish Tories have been touting my name as a potential defector for months now.
"So today, Im giving them what they want, but perhaps not for the reasons that they think.
"Leaving the party that I first joined when I was 15 is an enormous wrench, and Ive been through a lot of soul searching in the past few weeks."