It's impossible to avoid it for much longer. Some day very soon, probably Tuesday, there's going to be an election called, and we're all going to have to wrench our minds from pleasant things like holidays and lunch – and focus them on the uncomfortable subject of whom to vote for.

At the moment, David Cameron seems like the least awful option. He has nice pink cheeks and a vision of a rejuvenated England full of can-do Blitz spirit. A few days ago, Dave unveiled his grand plan: a "Big Society" with less power for politicians and more for communities; a country full of good people really pulling their weight, supported, not hectored, by the state. And to my surprise most newspapers greeted this notion with applause. Don't dismiss it just because it's a Tory idea, said The Guardian. "Cameron's plans poses a genuine philosophical challenge to the Labour party." Well, yes, The Guardian is right, we've had enough cynicism; yes, it's time to believe in Britain again. But I'm afraid, before we all tick the Tory box, I have two little buckets of cold water to tip over Cameron's victory parade.

The first bucket comes marked with the letters CRB. CRB stands for the Criminal Records Bureau and it's shorthand for the registering and checking process that everyone who wants to work with children or "vulnerable" adults now has to go through. A new super-charged CRB check was introduced after the Soham murders with the noble aim of stopping paedos. But instead of protecting children, its sole effect has been to snuff out Britain's charitable instinct.

The CRB means millions of forms have to be filled in, signed and countersigned; millions of processing fees paid before anyone can legally do a good turn. Millions of volunteers are put off before they even start, and if they persevere, they often find their form is lost or delayed. Of those who have made it through, thousands have been wrongly labelled as criminals, and suddenly found their lives in tatters.

CRB has become not just a legal requirement but also a mindset. Last weekend a friend of mine was stopped as he went to pick up his granddaughters from the school swimming pool. "You'll have to wait for someone to accompany you," said a teacher. He said: "But you know me. I've been picking the kids up for years." No dice. Better safe than sensible any day: that's England's motto.

If, like Gordon Brown, you secretly believe that the state should provide everything, that pesky volunteers should be sent back home to play Wii like everyone else, then CRB checks are a godsend. But for a government that believes in local activism – for the Cameroons – they are a disaster. They're guaranteed to act like super-strength weed-killer on any grass-roots movement.

Cameron has been building his picture of a Big Society for four and half years now, he says. If he was really serious about encouraging local people to fix local problems, there'd have been a Tory task force set up years ago to figure out how to kibosh the CRB. And was there? Nope.

Yes it's true there's been some Tory tutting and head-shaking about CRB checks. But axeing the CRB is a tricky proposition. It means toughing out criticism from sections of the press: "Tories put our kids at risk"; it might require a firm new policy on sex offenders. It means interdepartmental co-operation between education, health and home.

"The big society demands a big social response, a mass engagement," said Dave C on Thursday, in the grip of his vision. "It means millions of people answering that noble question first asked by JFK: ask not what your country can do for you, but what you can do for your country." Well, I have a vision too. It's of Dave standing by a river pointing to a halcyon "Big Society" Britain over the other side. In my vision millions of eager citizens are rushing over the bridge towards this happy land, only to find that in the middle of the bridge there's a toll-booth marked CRB, endless tailbacks, and several people drowning in the water below.

My second bucket of cold water is more of a symbolic problem than a practical one. At the heart of the Tories' announcement was an ambition: "We want every adult to be part of an active neighbourhood group." So which active neighbourhood groups do you think Cameron is a member of? A friend of mine called his office to find out. The office couldn't even name one.