Lib Dem chief whip Andrew Stunell said Mr Oaten had stood down "with immediate effect" as home affairs spokesman.
"He has apologised to his family. He has apologised to his constituents who he always served well," Mr Stunell said.
Obviously not the only thing he was serving well. He always was a supporter of giving rides to young deviants.
Vaguely related : this rather wonderful post by Tommy G :
"We are all entitled to go about our lives free from assault and harassment. We are not entitled to universal affection, nor to approval."
UPDATE - BBC profile of Mr Oaten.
"He has strongly opposed ID cards, while on drugs"
What did he think of them when he came down ?