Former leadership candidate for the SNP, Ash Regan, has quit the party to join the Alba Party - becoming its first MSP.
Ms Regan, who got just over 11% of the vote in the race to succeed Nicola Sturgeon earlier this year, said the SNP has "lost its focus on independence".
Ms Regan said she could not "continue to be part of a party that has drifted from its path and its commitment to achieving independence as a matter of urgency".
"Sadly, it has become increasingly clear that the SNP has lost its focus on independence, the very foundation of its existence," she added.
Former SNP leader Alex Salmond, who set up Alba, said he was "delighted" to welcome Ms Regan, who is the MSP for Edinburgh Eastern.
He said: "Her commitment to the cause of Scottish independence has never been in question, and her addition to Alba sends a powerful message about the focus and determination we bring to achieving an independent Scotland.
"Having Ash join the Alba Party enriches our team and sharpens our focus on the immediate need for Scottish independence.
"She brings a level of commitment and principle that is deeply admired across Scotland, and I couldn't be more pleased to welcome her into our ranks."
It comes just weeks after MP Dr Lisa Cameron announced she was quitting the SNP to join the Conservatives.
Ms Regan had previously served as community safety minister in the Scottish government, but had quit that position last year so she could vote against controversial gender recognition reforms.
She then stood against Kate Forbes and Humza Yousaf in the race to succeed Ms Sturgeon.
Ms Regan, who was first elected as an SNP MSP in 2016, said it had been "an honour to serve the people of Scotland as an MSP and a minister".
As Alba's first MSP, Ms Regan said she would "take up the mantle of leadership for Alba at Holyrood".
In doing this, she vowed she would have a "clear focus on reinvigorating the cause of independence".