Mr Trump, who is seeking the Republican nomination for next year's presidential election, sparked outrage in the US after saying that there should be "a total and complete shutdown" of Muslims entering the US.
Speaking to a regular media briefing in Westminster, Mr Cameron's official spokeswoman declined to say whether Mr Trump's comments might lead to him being barred from entry to the UK under hate-speech laws.
But she said: "The Prime Minister completely disagrees with the comments made by Donald Trump, which are divisive, unhelpful and quite simply wrong," Britain-based ITV reported.
The White House, Hillary Clinton, former vice-president Dick Cheney and rivals for the Republican 2016 presidential nomination have lined up to criticize Donald Trump.