Radio Tonga reports a sugar shortage on Tongatapu and Vava'u.
A spokesperson for the Consumer Affairs division of the Ministry of Labour and Trade said the public can file complaints if they find shops selling sugar at inflated rates.
There are reports some places are placing a 20 percent premium on the set price.
The shortage had put down to uncertainty over shipping schedules.
A similar shortfall occurred last year.
There's hope a shipment of sugar will arrive next month.