The Prime Minister has launched a strong attack on the US whistleblower Edward Snowden and some newspapers for holding a "lah-di-dah, airy-fairy view" of the intelligence community.
He said that there are people in the world "who want to blow up our families" and that "what Snowden is doing and to an extent what the newspapers are doing" is helping such people to "evade" efforts to stop them.
"That is helping our enemies. Simple" he added.
More top news
The 100 leaders did not agree on concrete proposals, but the meeting has raised hopes for concrete international agreement next December.
The speech was OK, passionate at times and certainly well received, but did not display the passion of past speeches.
The brother-in-law of a British hostage being held by Islamic State militants in Syria, says he is scared by US airstrikes in the country.