Ex Tory right-winger Michelle Ballantyne will lead Nigel Farage's new Reform UK party in a move which means he now has an MSP at Holyrood.
Ballantyne quit the Scottish Conservatives in December after clashes with the leadership on policy and direction.
She provoked more controversy just days ago in a tirade against "collective madness" in the political response to the Covid-19 emergency.
Reform UK is a rebranded Brexit party. Farage previously led Ukip and campaigned for Britain quitting the European Union.
The appointment was confirmed in a live announcement by Farage's right-hand man Richard Tice, the party chairman.
Ballantyne was elected as a Tory on the regional list in the South of Scotland, which has given her the ability to switch to a new party without facing re-election. She has previously tried and failed to win election as leader of the Scottish Conservatives.
The next Holyrood vote in in May, although there are concerns lockdown could delay it.
Ballantyne said she will not "waste time" on independence and wants to keep taxation no higher than the UK levels.
Announcing the appointment, Reform UK said: "The SNP's agenda is increasingly unchallenged in Scotland. This lack of challenge is stifling creativity.
"The Conservatives, Labour and Liberals in Scotland have all failed to halt the SNP's grip on the country."
In a statment Ballantyne said: "Scotland has a rich history of entrepreneurs, inventors and thinkers. We have the collective strength and endeavour of the Union and the freedom of devolution to deliver a prosperous and exciting future for everyone in Scotland."
