The Media Development Authority (MDA) has reminded political parties not to produce and distribute party political films in the run-up to the general election.
It cited, for instance, the Singapore Democratic Party (SDP) clip Pappy Washing Powder and noted that such films are banned under Section 33 of the Films Act.
The MDA, however, said it would not be taking action as this was the first incident concerning a party political film and parties may not have been fully aware of the requirements under the Act.
Still, it added that it "will not hesitate to enforce the law firmly" if parties or candidates continue to publish such films.
The SDP clip, which is just over a minute long, was uploaded to YouTube on Aug 5.
Shot as a commercial for washing detergent, it shows a woman using washing powder named Pappy White to remove the words "transparency", "accountability" and "democracy" from T-shirts.
The MDA and the Political Films Consultative Committee found the clip to be a party political film.
In the letter that it sent to all political parties, the MDA also said that the law ensures "that political debate in Singapore is conducted in a responsible and dignified manner".
Films must not be used "to sensationalise serious issues in a biased or emotional manner", the MDA added.
The Films Act had originally banned all party political films, but the restrictions were partially lifted in 2009.
Changes to the laws then allowed certain types of political films, including live recordings of lawful events, commemorative videos and factual documentaries. The MDA said that political parties may consult it if they had doubts over what constituted a political film.