Tim Farron is quitting as leader of the Liberal Democrats saying he cannot carry on the face of continuing questions over his Christian faith.
He said he had been torn between his religion and serving as a political leader.
"The consequences of the focus on my faith is that I have found myself torn between living as a faithful Christian and serving as a political leader," he said.
"A better, wiser person than me may have been able to deal with this more successfully, to have remained faithful to Christ while leading a political party in the current environment.
"To be a political leader - especially of a progressive, liberal party in 2017 - and to live as a committed Christian, to hold faithfully to the Bible's teaching, has felt impossible for me."
The shock came just hours after the party's openly gay home affairs spokesman Lord Paddick announced he was quitting citing "concerns about the leader's views on various issues".
Mr Farron faced criticism during the General Election campaign for failing to answer questions about his position on homosexuality.
He made clear he supported equal marriage and LGBT rights, but in a broadcast interview did not say whether or not it was a sin.
After days of pressure to clarify his stance on the issue, he finally made clear he did not believe gay sex is a sin but continued to face questions in interviews.
In his statement, Mr Farron said the continued questions over his faith showed "we are kidding ourselves" if people in Britain thought they were living in a tolerant liberal society.
"I'm a liberal to my finger tips, and that liberalism means that I am passionate about defending the rights and liberties of people who believe different things to me," he said.
"There are Christians in politics who take the view that they should impose the tenets of faith on society, but I have not taken that approach because I disagree with it - it's not liberal and it is counterproductive when it comes to advancing the gospel.
"Even so, I seem to be the subject of suspicion because of what I believe and who my faith is in.
"In which case we are kidding ourselves if we think we yet live in a tolerant, liberal society. That's why I have chosen to step down as leader of the Liberal Democrats."