There was an excellent article on the FT website at the start of the month, which can be read here (however it is behind their paywall). I think it does an excellent job at removing some of the fallacies that surround immigration whilst at the same time admitting the problems it creates.
Firstly, there is the common complaint that people only come to our country in order to claim benefits. According to the data in the article if a migrant (from one of the A8 countries) is in the UK for more than two years there is a 20.2% chance they will be claiming a benefit (that means 4 in 5 aren't!) this compares with 39.7% of "native" Britons, almost double. In addition to this they are net contributors to public services, paying on average £1.37 of tax for every £1 of public service they use. Native Briton's are net users at £0.80 of tax for every £1.
These figures of course only from the A8 countries: Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Slovakia and Slovenia. The government can do nothing about this migration.
More importantly in my opinion was the details on the effect of income.
Particularly of interest is the graph on the left. This shows that there is a negative influence on wages of those who are in the lowest 20% of earners from migration. I guess this is intuitive as migrants are often willing to work for less. However above this figure it is actually positive. Remember, the government cannot do anything about European migration and has already stopped unskilled migrants from entering the country, therefore the policy of reducing the skilled migrants entering the country makes no sense.
The Tory policy is that of halving the net migration figures will therefore damage the economy. We have seen it with scientists who have been unable to obtain a visa and as such have gone to prestigious universities else where to continue their research. I am also witnessing it first hand at work, where a very hard working (normally the first into the office and almost always still there when I leave) and capable employee of Asian descent working for our Asia division is struggling to get a visa to continue to work in the UK. This is despite her being here for numerous years, earning all of her money and spending it here, paying taxes, speaking perfect English and building a life here. It would be wrong to say that a British person couldn't do her job, however I can't see them doing it better. Our business is helped by the fact we are a multicultural firm, with native French, Spanish, Italian, Swedish, Chinese and Czech employees, as most of our business is done in conjunction with the EC and with projects carried out in countries where it helps to have the local knowledge.
These skilled workers are going to be squeezed even more when you consider how feasible David Cameron's proposal is. Mark Easton posted an excellent blog on the BBC in August (here) which illustrates how much of our immigration is down to students. In a time where tuition fees is a hot topic, can we really turn away people who already pay more than £10k a year to study in our universities?
My opposition to the Tory policy however doesn't boil down to evidence of what is good or bad for our economy (though I think the evidence proves that the policy will be bad), it boils down a matter of principle. I am a liberal, I believe in people living the way they choose. The Liberal Democrats claim to be working towards removing any misfortune of birth, I see this as one of the biggest. There is a big wide world out there and I would hate for someone to tell me that I couldn't live where I wanted to just because I wasn't born there. Protectionism may (or may not) be good for a country but it is not good for the planet. All the divisions and secularism only builds walls between people, leading to discourse and hatred. We should be working towards a world (in this globalised age) where we are one community that respect other people's beliefs, traditions and customs.