A man has been charged after he allegedly sexually touched a teenager and performed an indecent act on a bus in Sydney’s inner west.

Police say a 17-year-old girl was walking at Marrickville, when she was approached by a man.

The girl ignored him and continued on towards a bus stop, where she was stopped again.

It’s alleged the man followed the teenager onto a bus, sat next to her and touched her inappropriately while performing an indecent act.

Members of the public went to the teenager’s aid and detained the 53-year-old until police arrived.

He’s been charged with several offences including sexually touch another person and carry out sexual act without consent.

He’s spent the night behind bars and will appear in Parramatta Local Court today.