For each person sleeping rough on London's streets, there are 13 more "hidden homeless" who sofa surf, sleep on buses, squat or have sex with strangers each night, a report said on Wednesday.

The London Assembly — an elected body that holds London's mayoral office to account — said more than 12,000 people do not have a home, often risking assault or abuse, but are excluded from official statistics and cut off from support.

"People sleeping on the streets of our city are just the tip of an iceberg," Sian Berry, chairwoman of London Assembly's housing committee, said in a statement.