The leader of Kingston Council has been arrested on suspicion of possessing indecent images of children.
Councillor Derek Osbourne was arrested at his New Malden home on Tuesday morning.
Councillor Liz Green, acting leader of Kingston Council, said: “Derek Osbourne has resigned from the Liberal Democrat group.
"We are deeply shocked by these allegations but I am unable to comment further as we must now allow the police the time and space they need to investigate the allegations thoroughly and without prejudice."
The Metropolitan Police said a 59-year-old man was arrested on June 11 at an address in Kingston, on suspicion of possessing indecent images of children.
He was taken into custody at a south London police station, and has since been bailed to a date in August, to allow further investigation.
Coun Osbourne was first elected in Kingston in 1986. He was deputy leader of the council from 1994 to 1997.
He first served as leader from 1997 to 1998 and again from 2003.