SINGAPORE, Feb 22 (Reuters) - Shares of Singapore's Wilmar International, the world's largest listed palm oil firm, fell as much as 9 percent in early trading on concerns about margins at its consumer business.

Wilmar had earlier on Wednesday posted better-than-expected fourth-quarter net profit as its expanded sugar operations made up for weakness at its core palm oil business.

By 9:06 a.m. (0106 GMT), Wilmar shares were down 8 percent at S$5.38, underperforming the Straits Times Index which was 0.3 percent lower.

"Quarter-on-quarter, we didn't really see improvement in margins. Although margins improved for oilseeds and grains, consumer pack continues to see lower margins," said Carey Wong, an analyst at OCBC Investment Research.

Consumer pack refers to products such as edible cooking oil, flour and rice.

"Even though they managed to raise prices for consumer pack a while back, it wasn't enough to outpace the costs of production," he said.

Wilmar earned $500 million in the three months ended December, a 57 percent rise from $318.6 million a year ago. (Reporting by Eveline Danubrata; Editing by Kevin Lim)