There's growing pressure on former Lib Dem president Tim Farron to lead his party after their devastating election results.
Following Nick Clegg's resignation last week party leaders in Scotland and Wales have jointly called on him to stand.
He's expected to be one of the front-runners to succeed Mr Clegg, along with Norman Lamb.
Nominations open on Wednesday - a winner should be revealed by mid July.
In a joint statement, Willie Rennie and Kirsty Williams said: "Thursday’s results were devastating for the Liberal Democrats.
"Our pain is eased by the knowledge that our liberal gains in government will endure.
"Despite our loss our party remains optimistic, hopeful and confident about what we can achieve on behalf of Britain.
"However, we now have to earn the right to be listened to again.
"To move forward we need a fresh start. With that in mind we call on Tim Farron to stand to be our next Federal Leader. We believe he is the right person to rebuild our Party, inspire and lead us into next year’s election campaigns. We will wholeheartedly support him if he decides to put himself forward.
"Tim is a committed liberal, a brilliant communicator, an outstanding campaigner and an inspirational leader.
"With him as leader we can show that we are a compassionate, tolerant, internationalist, reformist party that looks beyond sectional interest to the greater good, to our children's future not just ours, that believes in partnership home and abroad not division, that is liberal and democratic.
"We urge Tim to step up and lead our party to recovery."
10°C
10°C