It is an under-reported fact that Jesus wears a wristband bearing the slogan "What would David Cameron do?". Though the two men were born a couple of millennia apart, their relationship is essentially a time-travelling buddy movie – or rather it would be, if they weren't such ideological twins that you could scarcely slide a cigarette paper between their identikit personal philosophies.

It was all the way back in 2011 that the prime minister claimed that it was actually Jesus who founded his "big society" – which was something of a revelation, because up until then I think a lot of people had dismissed Christ for being a man without a really substantial idea.

This week, the PM returned to the continuum between the central tenets of Christianity and the policies of the coalition government with a sort of Gospel According to David Cameron – or the Book of Dave, if you will. His peroration came in response to a question from a member of the public, who may well have made the most savagely satirical inquiry of a politician since Tony Blair was asked in PMQs to "briefly outline his political philosophy".

"What would your response to Jesus be," this person asked Cameron, "on his instruction to us to sell all our possessions and give the proceeds to the poor?"

Well. I imagine this member of the public will soon be extraordinarily rendered to some Lynton Crosby-managed black site. Still, what a way to go.

As for Cameron's response, I don't need to tell you he declined to reply: "Jesus was a troublesome fundamentalist who barely appeared to have a job and appears to have naively placed pandering to the benefits class above economic growth on his list of priorities. I'd have told him to do one."

Instead, he released from his lips a ramble which, even in a perennially crowded field, must rank as the most ludicrous thing said by a politician this year. He struggles with the giving away bit, he began, but he's an active Christian, adding that "what I think is so good about Jesus's teachings is there are lots of things that he said that you can still apply very directly to daily life".

Go on. "Simple things, like do to others as you would be done by, love your neighbour as yourself, the Ten Commandments, the Sermon on the Mount …"

And the Lord saith: Do. Me. A. Favour. I know Anglicanism is the take-what-you-want-and-leave-the-rest buffet of world religion, but even by those standards Cameron's claim to be acting In His Name feels an elasticism too far. I accept he can't openly say, "Look, the way we're going to win this election is to hammer the poor, bring in Lynton Crosby – and, you know what? That's politics, baby." But pretending Jesus is basically a celebrity Conservative feels faintly unjustifiable.

The thing is, Cameron doesn't have to go around claiming to act in anyone's name – in fact, I expect most people would prefer he didn't. But if he's going to, perhaps it would make sense to familiarise himself with the texts cited. This is the sort of selective cobblers that could make even the Christian zealots of the US PGA Tour look consistent. (I do adore the multimillionaire golf evangelists: by night, they convene in ponderous born-again Bible study groups; by day they respond to their WWJD wristbands by doing things such as storming the 17th at Brookline like the least-sporting arses in golfing history.)

Before we go any further, I should say that I am no theologian, nor even a believer. But like many people over the age of eight or so, I am capable of reading the Sermon on the Mount – and, indeed, of hazarding a guess that Jesus would have been several million cubits to the left of any politician to grace our Westminster spectrum, from whichever party. I'm prepared to chuck Cameron a bone on his admirable adherence to the Ten Commandments – it must be a daily struggle to not go around killing and worshipping golden calves and whatnot. But either he hasn't read the Sermon on the Mount, or he's guilty of the most quarterwitted political misapprehension since Ronald Reagan heard Born in the USA and fancied it an uplifting hymn to the American Dream.

As for the "do as you would be done by" element of the PM's personal philosophy, it is on the things that matter most that I struggle to find him anything other than the most troubling of hypocrites.

When Cameron speaks of the emotional aspects of caring for a severely disabled child, which was his own tragic experience, he can move me and countless others to tears. But I am afraid to say that it is precisely his personal experience of that struggle that makes his hypocrisy on the practicalities of it for those infinitely less well-off than himself so completely, almost mesmerisingly, disgusting. It is unclear how he can visit cuts and privations on disabled people and parents of disabled people who – unlike him – lack the funds to make that heartbreaking and horrendous situation less of a practical struggle. Whether he lacks the imagination or the compassion to understand how the quotidian horrors of that life are made so much worse by the indignities of having to scrimp on nappies for doubly incontinent children and so on, I have no idea.

Perhaps he really does think all good Christians would prefer aircraft carriers to dignity for such people. Maybe there's something in the Sermon in the Mount to explain it all. But until the prime minister produces the relevant quote, I remain unpersuaded that he and Jesus are in this together.

Twitter: @MarinaHyde