On Tuesday night I spoke at a fringe event at the Liberal Democrat conference, which was co-hosted by FOREST and the excellent Liberal Vision. The subject was "Politics & Prohibition – how can liberals fight back against the nanny state?"

One point I stressed – and which I felt sure would endear me to a Lib Dem audience – was that we can't rely on a Conservative government doing much to fight the nanny state. On the contrary, what we're promised is an army of local directors of public health, dedicated public health budgets, a bigger, stronger chief medical officer's department, a "holistic strategy to focus public health across departments", "a clear marketing plan to promote healthy living", and a brand spanking new QUANGO – the Public Health Commission – to oversee it all.

There was even talk a while back about an 'NHS Health Miles Card', where people would get 'reward points' for losing weight, which they could then redeem against fresh vegetables, subsidized gym membership or even priority within other public services. That last idea – government systematically discriminating between citizens based on their lifestyle choices – strikes me as particularly disturbing, but it does seem to be the direction in which we are travelling.

All of this despite the fact that there's scant evidence that public health campaigns – especially those targeted at broad lifestyle issues like diet and exercise – work. Even the government's Wanless Review admitted as much, saying that public health campaigns have a ‘very poor information base’, that they exhibit a ‘lack of conclusive evidence for action’.

The trouble for the Lib Dems – and I made this point too – is that they are offering pretty much exactly the same thing as the Tories. And that's a real shame, because surely their role should be to stand outside the mainstream consensus, to offer something different and genuinely liberal.

Of course, the really irritating thing is that these so-called 'public health issues' are not actually public health issues at all. Public health is about securing health benefits that are by their nature public, like clean water and sanitation. It is not about what people freely choose to put into their own bodies. But since calling something 'public' legitimates having a public bureaucracy to deal with it, that's what politicians do. For me, this unopposed redefinition and erosion of privacy is the most worrying aspect of the debate.