Police have released images and launched an appeal for information after a man sexually assaulted a woman on a bus between Kingston and Epsom.

The assault happened on Friday, May 7, around 4.40pm, the Met Police, who are leading the investigation, said.

In their public information appeal a police spokesperson described how the victim, a 21-year-old woman, boarded a 418 bus in Kingston heading to Epsom at around 4.40pm, sitting down in the row of seats behind the exit doors by a window.

"A short time after sitting down, a man boarded the bus. He asked to sit next to the victim and she indicated that this would be ok.

"The man then put his hand on and started to touch her inappropriately on her leg.

"The victim stood up and moved, telling the suspect to stop touching her.

"Another passenger informed the bus driver who removed the suspect from the bus," the police appeal described.

A CCTC image was subsequently released by the Met depicting a man they are now "keen to identify" in relation to the assault.

Detective Chief Inspector Michael Dougall is working on the case.

"If you recognise this man or have any information about his whereabouts, please contact police right away," he said. "It is vital we identify him. No piece of information is insignificant and could help us in our investigation."

Anyone who can identify him is asked to tweet @MetCC or call 101 referencing CAD 1209/17AUG.

To remain 100 per cent anonymous, contact the independent charity Crimestoppers on 0800 555 111.