The Singapore Heart Foundation (SHF) has filed a police report after learning that a group it did not authorise claimed to be collecting donations on its behalf at Bugis Junction on Sunday.
The foundation said the "volunteers" had its flag day stickers and claimed to represent the charity.
SHF chief executive Vernon Kang said yesterday: "We would like to inform the public that the SHF has not commissioned any volunteers to carry out fund-raising activities on the said date or at the said venue."
In response to queries, he said a member of the public who was approached by one of the "volunteers" on Sunday had alerted the foundation.
"The 'volunteer' claimed to be raising funds for low-income students and former convicts - which is not aligned with the SHF's mission," said Mr Kang.
"The SHF does not collect cash donations, and all donations can be done only via the Direct Debit Donor Programme. Furthermore, the 'volunteer' had only a student ez-link card on him for identification purposes."
The SHF is a decades-old non- profit charitable organisation working to promote awareness of heart disease.
Mr Kang said people can verify volunteers' identities by looking out for an identification badge and a Collectors Certificate of Authority issued by the National Council of Social Service when approached for donations.
The police report filed by the SHF included the account of a donor who had asked for a receipt or verification from a "volunteer" after giving $10, and was shown a letter saying the "volunteer" was from a private company.
The Straits Times contacted the company's director, who said it runs events and roadshows, but also does street sales of trinkets such as stress balls and luggage tags. He denied allegations that his staff had used the SHF's name to canvass donations or make sales.
At Bugis Junction yesterday evening, no "volunteers" claiming to be from the SHF could be seen. The police confirmed that a report had been made.