Lifeguards have helped foil the attempted abduction of a seven-week-old baby from his mother's side at a Sydney beach.

The baby boy was lying on a towel next to his 31-year-old mother at Bronte Beach on Monday at about 6pm when a 38-year-old man approached and tried to grab the child.

The mother pushed him away and suffered minor injuries as she struggled with the man before lifeguards stepped in.

The man was refused bail and is expected to face Waverley Local Court again on February 16 charged with attempted child abduction and common assault.