London School of Economics academic Philippe Legrain tells the Lords economic affairs committee why he thinks immigration boosts the economy.

Responding to a Migration Watch report - and the Lords' committee's own 2008 report suggesting that immigration does not increase the wealth of the existing population - he says that migrants boost productivity and average wealth because they are usually of working age and are entrepreneurial and even low-skilled workers - such as a cleaner - allow highly skilled professionals to work longer hours.

Watch Migration Watch's Lord Green giving his evidence to the committee