James Frayne is Director of communications agency Public First and author of Meet the People, a guide to moving public opinion.

As I’ve occasionally pointed out on this site, while it was common for Conservative MPs in the 1990s to define themselves by their belief in a small state, most new parliamentarians are strong advocates for state action to solve societal problems, and there are now very few Conservative MPs who could even vaguely be described as libertarian. These pages regularly contain commentary from MPs that would have looked odd two decades ago. And without the lead of politicians, who have the ability to inject ideas into the political bloodstream and keep them there, there is a strong danger that libertarianism withers in the rest of the country. It appears this could be happening now.

My agency, Public First, commissioned the rising new polling agency Delta Poll to look at public attitudes towards the issue of childhood obesity. We chose to to look at this area as it’s a highly-charged policy field in which debate is strongly testing politicians’ vision on the limits of the state. The results might surprise regular readers of this site – because Conservative voters are often the most enthusiastic for state intervention.

Asked which explanations for childhood obesity people found most persuasive, the top answer for the general public and for Conservative voters was “parents feeding their children poor diets”, while the second top answer for both groups was “convenience food being too full of sugar and fat”. The third answer for both was “fast food businesses deliberately targeting advertising at children”. But the interesting point in this set of answers is that Conservative voters were much more likely to blame these private businesses than either Labour or Lib Dem voters. They were effectively the most critical of private business – even though many such businesses would reasonably claim that they did emphatically did not target ads at children.

This hard line against business from Conservative voters was visible elsewhere. While the public’s top policy option to tackle childhood obesity was “banning all food advertising targeted at children” Conservative voters were the most enthusiastic about this policy option. They were also more enthusiastic than the other main parties’ voters for the country’s fifth most popular option: “forcing takeaways near schools to close”. 35 per cent of Conservatives chose this option, compared to just 21 per cent of Labour voters and eight per cent of Lib Dems. And while Conservative voters said parents were mostly to blame for their children’s weight, they were still at least as likely as other parties’ voters to blame food manufacturers.

Admittedly, with polls like this, it’s hard to say for sure that things have definitely changed. After all, there’s no tracking data – and issues-based polls like this are rare. However, it’s none the less surprising that Conservative voters are as comparatively tough on private businesses as they appear in this poll. Yes, parental responsibility effectively comes top – but Conservative voters are still sympathetic to action that libertarian and small state campaigners would consider to be from the Nanny State.

Can we put everything down to the lack of senior Conservative politicians making the case against state intervention? I think very substantially. But private businesses take at least as much responsibility. They have been largely passive in the debate on the merits of Government intervention over the last 15 years, largely positioning themselves on the side of state action – but simply to a lesser extent. They haven’t made a public case that politicians should stay out of business, nor have they united behind other policy alternatives.

There’s a tendency in politics – even after the turbulence of the last five years – to assume that public opinion and politics generally tends to stay in basically the same place. This is surely wrong. If there are few advocates for particular policies you can’t expect public attitudes to remain static. While such think tanks as the IEA, the CPS and the ASI have been leading the charge against the big state, they have done so amid an onslaught of attacks from state bodies and NGOs. Without high-profile politicians taking up the battle it’s hard to see how the sort of numbers highlighted in this poll will do anything but move towards action.