The Tories are up to their old tricks. In the Times, Tim Montgomerie calls on Cameron to "turn the issue of immigration into an issue of fairness for the working class." He says:

For the people at the bottom of the pile the impact [of immigration] has been enormous...The flipside of cheap nannies, cleaners and painters for the well-to-do in Hampstead and low-cost waiting staff for the hospitality industry is a struggle to make ends meet for hundreds of thousands of low-income British families.

But how "enormous" is enormous? Mr Montgomerie doesn't give us any numbers. The largest reputable estimate of an impact low-skilled wages I've seen comes from Jumana Saleheen and Steve Nickell:

A 10 percentage point rise in the proportion of immigrants working in semi/unskilled services ' that is, in care homes, bars, shops, restaurants, cleaning, for example ' leads to a 5.2 percent reduction in pay.

However, a 10 percentage point rise is a big rise - a near-doubling: in their data sample, these industries have immigrant proportions of around 12%.

Even if this is right, it does not justify restricting immigration. Insofar as the "well-to-do" gain from immigration, it is instead a case for a more redistributive tax and benefit system, to spread the gains more equitably.

What's more, immigration is not the only - or even main - reason why hundreds of thousands of low-income families are struggling to make ends meet. There's also the recession (since January 2008 real average earnings have fallen 7.6%, a bigger decline than even Nickell and Saleheen's estimate of an immigration effect); the impact of technical change and globalization in reducing the wages and job prospects of the unskilled; and of course the rising power of the capitalist class.

But Mr Montgomerie omits any mention of these. It's rather queer for someone to care so much about the fate of unskilled workers in the context of immigration, and yet be indifferent about the many other threats to their well-being. It's enough to make one suspect that something else is going on.

That something is the same thing that we're seeing in the Tories adverts attacking people "who won't work." It's a crass and largely fact-free exercise at divide-and-rule, an attempt to turn natives against migrants and those in work against those out of work, thus disguising the fact that all four groups have common concerns.

In fact, I fear it's worse than that. The cultivation of animosity to foreigners, and a glorification of virtuous hard-working indigenous people has a whiff of fascism about it.