It's more than just immigration; certain immigrant cultures have large families, wherever they live, and the willingness of the UK Government to give them benefits for nothing only encourages them to procreate. The same goes for the "underclasses" who see children as a form of income. If the benefits system were overhauled, I think there would be a significant drop in the number of immigrants and also the scroungers in this country who just breed like rabbits for the amount of state handouts they get.