Jo Swinson has won the Liberal Democrat leadership race in a landslide, defeating Sir Ed Davey by nearly 20,000 votes.
The East Dunbartonshire MP received 47,900 votes compared with Sir Ed who garnered 28,021.
She said she was “delighted, honoured, absolutely over the moon” to be chosen as leader and was “ready for the fight of our lives”.
The former party deputy joined Parliament at the age of 25 and was a business minister in the Lib Dem-Conservative coalition government.
In her victory speech she pledged to stop Brexit “whatever it takes”.
“You have put your trust in me not only to lead our party but also lead and grow the open liberal movement that our country so desperately needs,” she said.
“As your leader I will do whatever it takes to stop Brexit. It’s the Liberal Democrats who can lead the renewal that our country needs.”
The party is buoyed by its best ever results in the European elections, and Ms Swinson said “liberalism is alive and thriving”.
It has positioned itself as the anti-Brexit party and has pledged to turn away any defecting Conservative MPs unless they take an anti-Brexit stance.
Ms Swinson used her first speech as leader to slam Tory leadership frontrunner Boris Johnson.
“Tomorrow we expect Boris Johnson will take the keys to Number 10. But he has shown time and again that he isn’t fit to be PM. Boris Johnson only cares about Boris Johnson,” she said.
“Brexit was about who we are as a country. If feels like our liberal values are under attack. We champion freedom, but Brexit will mean the next generation is less free.”