Research by the South China Morning Post supports claims that asylum seekers may be getting less food than stated by the organisation contracted by the government to provide it.
The investigation, based on complaints from refugees and their union, has prompted calls from non-governmental organisations and human-rights lawyers for an overhaul of the support system for asylum seekers.
A group of asylum seekers staged sit-ins and hunger strikes at ISS offices last week in protest.
The Post visited several shops across Hong Kong with a list of foods provided by International Social Services Hong Kong. A comparison found that buying the goods on the lists would cost between 13 and 30 per cent less than the HK$1,060 worth of food ISS was contracted to provide.
ISS-HK denies any wrongdoing, saying its food costs were affected by the high price of speciality items such as basmati rice and halal meat, needed to cater for refugees, most of whom are from South Asia and Africa.
Executive director of the Hong Kong Refugee Advice Centre, Aleta Miller, said food pricing needed to be more transparent.
"But the bigger issue here is that the model is fundamentally flawed," she said. "Currently, refugees are forced to collect food in kind: they have to physically pick up bags of food and carry them home, which means less choice, high overhead costs and more [susceptibility] to problems with quality and pricing."
Miller said refugees sometimes had to eat rotting food.
ISS-HK last week supplied an annotated photograph showing the monthly food order of a 21-year-old Ugandan man.
Using those details the Post visited the Kai Bo Supermarket, wet markets and speciality food stores in Causeway Bay, Wan Chai, Chungking Mansions and Sham Shui Po to collect a list of retail prices for the goods.
The government is legally obliged to provide adequate nutrition and housing to refugees.
But last week, a refugee union claimed only HK$600 to HK$700-worth of food was distributed, rather than the HK$1,060-worth required for each adult per month.
The union sought a price list, which both ISS-HK and the Social Welfare Department declined to provide, saying it was a confidential tender document.
The union wants asylum seekers to be allowed to work while their claims are processed, and be given supermarket vouchers instead of groceries.
The Court of Final Appeal ruled on Tuesday that asylum seekers did not have the right to work in Hong Kong.
The department last week denied any irregularities, saying the tender prices were not comparable to products on the regular retail market as vendors were not allowed to change the price of items during a contract period.
"The aggregated prices of the food items provided … per month amounts to the food allowance," the department said. The average allowance, it added, did not include ISS-HK's administrative costs but it did not say whether it included the vendor's administrative costs.
"If the government chooses to go with a provider that has higher prices than other retail shops it can do that legally," said Patricia Ho, a lawyer with human-rights practice Daly and Associates. "Whether they're acting wisely, that's a different question."
"The system set up has huge problems," said Mark Daly, a partner in the firm. "The needs of the claimants are not being met. They should be fitted into the proper welfare system."
In recent years, ISS-HK has come under scrutiny over the conditions asylum seekers are living in, some without toilets or fresh drinking water.
The Hong Kong branch of the Swiss-based global aid network was commissioned by the department in 2006 to take care of asylum seekers. NGOs say it serves about 5,000, providing food, toiletries and allowances for accommodation and transport costs.
The amount for groceries increases to HK$1,200 this month after government nutritionists deemed an increase necessary.
Vision First, an NGO that has helped the refugee union organise has previously expressed interest in taking over the contract from ISS-HK, but recently said it would like to see the department take on the responsibility.