This ippr briefing is an attempt to work through the implications of a cap on immigration to the UK.

As we approach a general election, all three main parties are keen to emphasise that they would be tough on immigration. The Liberal Democrats talk about a 'firm but fair system'; Labour emphasises its 'tough but flexible' Australian-style Points-Based System. But the Conservatives have gone a step further and have made a cap on immigration a headline policy. Although they have not set out the level at which such a cap might be set, they have talked about reducing annual net immigration below 100,000, and have also intimated their support for calls for annual net immigration to be reduced to around 40,000.

We should state from the outset that we think that a cap would be a bad idea, both in political and policy terms. We believe that immigration policy should be based on an assessment of the costs and benefits of migration, and on more effective communication with the public, rather than on a (more or less) arbitrary number. However, a cap is much discussed in the current political debate, and it is important to understand the implications of imposing one.