Asked yesterday during a visit to Bentley's headquarters in Crewe why Britain let in immigrants who were a "constant drain" on public services while others "work hard", David Cameron replied : "I basically agree with you. There are some benefits from being a country that welcomes people who want to come here and work hard.
"But in the last decade we have had an immigration policy that's completely lax. The pressure it puts on our public services and communities is too great."
Even by the baleful standards of this government, Cameron's agreement that immigrants are a "constant drain" on the UK is remarkably at odds with the facts. As every study on the subject has shown, migrants contribute far more in taxes than they receive in benefits and services. An OECD report  last month, for instance, found that they make a net contribution of 1.02 per cent of GDP or £16.3bn to the UK, since they are younger and more economically active than the population in general.
In the case of welfare, despite the scaremongering rhetoric of "benefit tourists", the DWP's own research found that those born abroad were significantly less likely to claim benefits than UK nationals. Of the 5.5 million people claiming working age benefits in February 2011, just 371,000 (6.4 per cent) were foreign nationals when they first arrived in the UK. That means only 6.6 per cent of those born abroad were receiving benefits, compared to 16.6 per cent of UK nationals.
It's for these reasons, among others, that, as the Office for Budget Responsibility showed last week , we will need more, not fewer immigrants, if we are to cope with the challenge of an ageing population and the resultant increase in the national debt. Should Britain maintain net migration of around 140,000 a year (a level significantly higher than the government's target of 'tens of thousands'), debt will rise to 99 per cent of GDP by 2062-63. But should it reduce net migration to zero, debt will surge to 174 per cent. As the OBR concluded, "[There is] clear evidence that, since migrants tend to be more concentrated in the working-age group relatively to the rest of the population, immigration has a positive effect on the public sector’s debt…higher levels of net inward migration are projected to reduce public sector net debt as a share of GDP over the long term relative to the levels it would otherwise reach."
One would expect a fiscal conservative like Cameron to act on such advice but, as so often in recent times, the PM is determined to put politics before policy. Britain and its public services will be all the poorer for it.