Many (young) Chinese S'poreans don't have Mandarin as a mother tongue in reality! This is borne of current (2000) census statistics which indicate that 23.9% of Chinese aged 5 and up speak English most frequently at home, following 30.7% who speak "dialects". Mandarin is most commonly spoken at home by 45.1% of the Chinese population aged at least 5 y/o (source:
http://www.singstat.gov.sg/pubn/pape...-literacy.pdf).
Btw, what is the meaning of "misread or mispronounce" Chinese words? Many native speakers I know of in China/Taiwan and elsewhere do exactly the same thing, but no one questions their proficiency, much less have the audacity to make so bold a (prescriptive) claim that they "cannot speak their mother tongue properly", for whom Mandarin is indeed a mother tongue. Mind you, "properly" according to what/whose standards? If you're comparing "speaking Mandarin properly" with codeswitching in Mandarin/any language and another language (including Singlish), then you're just comparing apples (speaking in one language completely, usu as a result of being functionally monolingual) and bananas (codeswitching as a result of being bilingual, altho not nec functionally so).
And btw, don't obfuscate the issue by calling it "Chinese". What exactly is "Chinese"? Aren't Hokkien and Cantonese "Chinese"?
Asking the "authorities" to look into the matter is as good as going up to anybody who speaks "Chinese improperly" and correcting the person as such. Let's see what the success rate is. I'm not betting on it.