Over 100 restaurants feature discriminatory rules and notices against mainlanders, according to a survey by the Society for Community Organization.
Many of them refuse to receive mainland customers or anyone who speaks in Putonghua, blaming the outbreak and the government's refusal to close all checkpoints.
In an investigation carried out between February 15 and 28, the group identified at least 101 restaurants that explicitly said they didn't welcome mainlanders or those who speak Putonghua.
It also visited 61 restaurants, finding 38 had notices saying mainlanders were not welcome. Workers from five restaurants were also witnessed barring mainlanders.
Several restaurants also barred unmasked customers and anyone who had visited the mainland in the past 14 days.
Other discriminatory acts included requesting customers present HKID cards first, and selectively serving Putonghua-speaking Taiwanese visitors only.
Community organizer Wong Chi-yuen said it is understandable for restaurants to ban customers with apparent symptoms, but a clear-cut ban against all mainlanders is "obviously discriminatory."
The group said the Race Discrimination Ordinance only constrains people from discriminatory acts based on race, skin color, descent and ethnicity.
"Although the situation may not be seen as a violation of the ordinance, it doesn't imply the acts are reasonable," Wong said, saying the restaurants could cause "indirect racial discrimination" as they imposed restrictions on customers showing "differences in languages."
He urged the government to amend the law to also place more consideration on "nationality" and "resident status."
The Equal Opportunities Commission said it "acknowledges the survey results" and is concerned over the issue.
The EOC earlier advised a restaurant chain, Kwong Wing Catering, to remove notices of "serving Hong Kong people only" that was posted outside its outlets last month.
The watchdog said that a discriminatory act is unlawful "when a service provider has a particular policy or way of working that puts a certain racial group at a disadvantage," but did not reveal whether any action had been taken against the catering group due to "confidentiality" issues.
Wong said the EOC should handle the case step by step, and allow time for restaurant owners to fix the discriminatory issue.
"But if the problem is not solved, it should consider taking further action, otherwise the ordinance will just be an empty shell," he said.