Isn't it wonderful? Refugees from the war-torn lands of Syria and Iraq, most of them Muslims, are becoming Christians in large numbers thanks to the welcome they've received from churches in their host countries.

Christians might well feel encouraged by this. But here's the problem. How many of these people are genuine converts, and how many are calling themselves Christians because they think it'll make their claims for asylum more convincing? After all, everyone knows how converts have been treated by Islamist extremists. No one could be so heartless as to send someone who publicly declares their new faith back to a situation like that.

Consequently, another problem: how do you tell the difference between a genuine convert and someone who's just using religion as a convenience?

According to immigration officials, it's simple. You ask people to reel off the Ten Commandments. If they can't they obviously aren't genuine Christians. Or here's a good one: what colour are Bibles?

The all-party parliamentary group on international religious freedom is releasing tomorrow what looks like, on the basis of details leaked so far, a damning report into how assessors are treating people who claim to have converted. These caseworkers are asking questions aimed at establishing whether people's faith is genuine, and in doing so – without any training, insight or the remotest understanding of how religion actually works – they risk denying genuine Christians asylum.

Both of the examples cited above are genuine questions asked of asylum seekers. Here's a confession: I'm a Baptist minister, and if I were faced with a panel of hostile questioners whose decision could determine my entire future I'd struggle to name all the commandments, at least in the right order. I'm sure I could get them all, with the aid of my fingers, but I doubt if I'd be fluent. As far as Bibles, go, the answer they're looking for is presumably black, but they'd be rather puzzled by the multicoloured array on my shelf at home.

To be fair, it's not the Home Office's fault. Its guidance is in fact rather sensible. In assessing religious conversion, it says: "What is being assessed is primarily whether the claimant has genuinely moved towards a firm decision to leave the faith of their upbringing and become a Christian. To be credible, something so potentially life-changing should not be perfunctory, vague, or ill-thought out."

It makes a point of saying: "Although the person's understanding of the faith and of the particular Christian tradition the claimant has joined (if any) is relevant, caseworkers are not qualified to assess the accuracy or relevance of answers to more than the most basic knowledge questions (another reason for not overdoing that line of questioning at interview). But statements of belief or answers to specific questions which are so clearly wrong that no reasonably well-informed person could be expected to take them seriously will call into question the credibility of the conversion."

Yet it appears to be precisely this that caseworkers are doing, setting themselves up as inquisitors on the basis of an understanding of religion that would be laughable if the consequences weren't so serious.

For the avoidance of doubt: the genuineness of a person's conversion cannot be judged by whether they can reel off answers to questions they could have learned from Wikipedia, and still less by questions based on half-remembered cultural clichés like Bibles being black. Converts might not have had much teaching, if any. They might not have been able to worship regularly. They might not have had a Bible at all. But they have been sincerely drawn to Jesus Christ and are prepared to put their lives on the line for their new faith. The idea that their heartfelt commitment to him can be so casually dismissed by a religiously illiterate civil servant is a scandal.

No one doubts that it's important to distinguish true believers from pretenders, though the number of false claimants is likely to be quite small, given the potential consequences of rejecting the faith of their birth. But it is not converts who are abusing the immigration system here, but the actions of those who are so determined to keep them out that they deliberately exceed their authority and flout the guidelines under which they are supposed to operate. Ultimately, this is a question of how the Home Office manages its staff. Now, if ever, it needs to prove it is fit for purpose.

Follow Mark Woods on Twitter: @RevMarkWoods