SYDNEY, Aug 18 (Reuters) - Australia's competition regulator said on Thursday that Qantas Airways Ltd's proposed purchase of the remainder of charter operator Alliance Aviation Services Ltd for A$610.8 million ($423.41 million) raised concerns.

"We are concerned that this proposed acquisition is likely to substantially lessen competition for air transport services to and from regional and remote areas in Queensland and Western Australia for corporate customers," Australian Competition and Consumer Commission (ACCC) Chair Gina Cass-Gottlieb said in a statement. ($1 = 1.4426 Australian dollars) (Reporting by Jamie Freed; Editing by Muralikumar Anantharaman)