Steven Purcell, the Labour leader of Glasgow city council, has resigned after almost five years in office.
The 37-year-old is said to be suffering from stress and will be replaced by his deputy, Jim Coleman, until a successor is elected.
Mr Purcell, who is openly gay, was ranked at number 16 last year on PinkNews.co.uk’s 50 most powerful gay, lesbian and bisexual people in British politics.
He has been tipped as a future leader of Scottish Labour and is the most powerful gay man in Scottish politics.
He tendered his resignation yesterday.
His spokesman Jack Irvine said: “Steven’s family and close friends came to his home at the weekend. They were deeply concerned about the enormous stress levels he was displaying.
“Steven agreed that the pressures surrounding the SPT [Strathclyde Partnership for Transport] debacle and the Commonwealth Games were enormous and that he was totally exhausted.
“He agreed he needed counselling and medical care.
“Steven hopes that the people of Glasgow appreciate that he’s worked so hard for the city he loves.”
Mr Purcell has been under pressure over the Strathclyde Partnership for Transport. A row over expenses has led to three senior figures resigning.
A Scottish Labour Party spokesman said: “We respect Mr Purcell’s statement indicating that he intends to resign and so the Labour group on the council will meet today to ensure that all its business can be properly carried out.
“We hope Steven makes a full recovery.”
A councillor since 1995, Mr Purcell was elected, unopposed, as leader of Glasgow city council in May 2005 at the age of 32. He came out in 2006.