There's skill shortages in this country which we seem not to be able to fill with people from this country. I think that we need to look at the scope of apprenticeships and work with Colleges/Universities to make sure that going forward we have people with the correct skill sets to bridge the gap.
In the meantime, where do we get those people from?
Also, we are going to get an increasingly ageing population, we are going to need younger workers at some point to generate income in this country.
Yes, we don't want people to come to this country simply to scrounge on benefits, I believe however that will be a minority of people however (although I'm sure the Daily Mail / UKIP will highlight every single case individually in an attempt to distort people's perceptions of what's really going on).
Block immigration at your peril, this country will suffer economically if you do.
A very high proportion of doctors and nurses at our local hospital are immigrants, as are many of the other skilled professionals working there. As they gain experience they naturally move on to make progress in their careers. If we block immigration who will replace these skilled people the NHS so desperately needs.