Of course the "net" migration figures are disingenuous - unless, that is, you are happy to see the UK's population swapped by losing predominantly high skilled or high value people and replacing them with predominantly low skilled or low value people. (I know there are exceptions to these generalisations, but that's the main thrust of "net" immigration).
However, that's by the way. In 2013 450,000 non-British people arrived to settle in the UK. Of these 201,000 came from other EU countries. Neither Mr Cameron nor indeed anybody else has any control whatsoever over this 45% of new arrivals. So sp is quite correct. Since none of the main parties (including the Conservatives) or combinations thereof has any real intention of steering the UK out of the EU, nor any realistic prospect of "renegotiating" the issue of free movement of people, we're stuck with it.
I think their best chance of reducing net immigration is to try and drive as many British people as they can out of the UK. They seem to be making quite a good job of that.