A point based system for immigration used by Canada, New Zealand, Australia and loosely used in the UK. The problem is not using a points based system as it is already in place, but it is not controlled or structured the same as the other nations.
The problem is simple, in a nutshell, The European Union freedom of movement.
The Freedom of movement and right to work anywhere within the European Union is a fundamental freedom of the EU member states, it is also the cause mass immigration into the UK and we cannot control who comes in [over 20 million unemployed in EU and rising). So in effect, there are controls on immigration outside of Europe but none within it. Yes. But it is more serious than that.
The European Union is only as strong as its weakest border or embassy of its 28 Member states. If any one of the Countries or Embassies for whatever reason issues EU passports to any person outside of the EU they cannot be challenged.
As an example if the UK has a point based system and is surrounded by water as an effective border control, “Italian embassy” in Brazil issues passports to Brazilians. They can then fly direct to the UK and work with no challenge or points based system.
Fact: I worked on a building site in London where several Brazilian men had EU Italian passports and had never set foot in Europe before, only one of whom spoke English.
If we leave the abuse of the system alone and concentrate on “normal” immigration, I would like to reference a discussion paper commissioned by the EU http://www.zei.uni-bonn.de/dateien/discussion-paper/dp_c217_kraleva.pdf