The Liberal Democrat leader has called on Theresa May to resign and said plans for Brexit should be put on hold after the Conservatives suffered bruising losses at last night's election.
Tim Farron said Mrs May had called an election from "sheer arrogance and vanity" while "expecting it to be a coronation".
He said she "took each and every one of us for granted" in a speech this morning.
Theresa May promised strong and stable leadership. She has brought weakness and uncertainty. If she has an ounce of self-respect, she will resign.
Mr Farron, whose party campaigned heavily on a pro-Europe platform, also said that the negotiations for Brexit should be put on hold until the new government had reassessed its position.
Theresa May is expected to receive a frosty reception when she meets the 1922 Committee later. But what do we know about the group?
The Prime Minister appointed her former leadership rival as Environment Secretary as she confirms her new top team.
He insisted he would be backing Theresa May as leader and has warned MPs to "calm down and get behind the Prime Minister".