I noted last week that the decision by the London mayoral candidates to publish their tax returns had set an important precedent that other senior politicians would feel compelled to follow. Since then, George Osborne has said he is "very happy" to consider publishing ministers' tax returns and, now, David Cameron has followed his Chancellor's lead. A source tells the Daily Telegraph:

The Prime Minister is relaxed about the idea of the tax returns of senior Cabinet Ministers being published, but wants the opportunity to explore how this might work

But would Cameron's tax return be enough to satisfy the new demand for transparency? In a significant intervention, David Davis has rightly argued that any proposal should also cover the disclosure of wealth and assets:

This will induce the politics of envy – but if you are going to do it, you have got to cover everything: wealth, trusts, whether you are a beneficiary of trusts, whether you are going to inherit things.

If you want really to know about someone’s tax affairs you have to know about more than just someone’s tax return. You have to know their assets, the potential inheritances, if they are going to be the beneficiaries of upcoming trust funds – all those things.

Among other things, this would draw further attention to Cameron and Osborne's privileged status, an ever more sensitive issue since the abolition of the 50p tax rate. Osborne, for instance, owns a 15 per cent stake in his family's wallpaper company Osborne & Little and stands to inherit around £4m from a trust fund, while Cameron's wealth is estimated at £3.2m (excluding inheritance). Indeed, the latter once memorably admitted to the Times that he couldn't remember how many houses he owns.

Here's the full exchange:

So how many properties do you own? “I own a house in North Kensington which you’ve been to and my house in the constituency in Oxfordshire and that is, as far as I know, all I have.”

A house in Cornwall? “No, that is, Samantha used to have a timeshare in South Devon but she doesn’t any more.” And there isn’t a fourth? “I don’t think so – not that I can think of.” Please don’t say, “Not that I can think of.” “You might be… Samantha owns a field in Scunthorpe but she doesn’t own a house…”

The rest of the interview was punctuated with Cameron’s nagging anxiety about how this exchange was going to make him sound: “I was wondering how that will come across as a soundbite”; “‘Not that I can think of’ makes me sound… I am really worried about that…”; “I am still thinking about this house thing”; and his parting shot was: “Do not make me sound like a prat for not knowing how many houses I’ve got."

Davis, who recently observed that Cameron and his ministers ("very well turned out, well-fed") "look like they’re in a completely different world", will have his own motives for demanding greater transparency. Ever since he fought Cameron for the Conservative leadership in 2005, Davis has rarely missed an opportunity to contrast his humble background (he was raised on a council estate in Tooting) with that of the Eton-educated Cameron.