SYDNEY—A consortium led by Brookfield Asset Management raised its takeover offer for Australia’s Origin Energy to around US$10.50 billion, but again ran into opposition from a big investor who thinks it is trying to buy the energy retailer and generator on the cheap.

Origin on Thursday said the Brookfield-led group is now offering 9.53 Australian dollars (US$6.10) per share, which values the company at A$16.41 billion. The revised offer is some 8% higher than the cash consideration of A$8.81 per share outlined in bid documents when Origin agreed to the acquisition in March.