In the continuing saga of the redacted flat tax documents, the issue is whether or not the Treasury used a Section 36 examption to the Freedom of Information Act to redact the documents that were reported in the Financial Times.

If it was s36, a minister would have authorised it. If not, the Daily Telegraph, got its story about the redactions wrong. The Information Commissioner’s guidance on section 36 (PDF) explains all this if you want the technical nitty-gritty.

Bishop Hill has been trawling the statute book and has a theory about what I’ll find when I get a reply to my follow-up FOIA request:

While there are indeed 22 exemptions as possible candidates, many can be discounted immediately — for example the national security exemption or disclosures which might affect foreign relations.

Of the remaining exemptions, the most likely candidates look like s34 Parliamentary privilege and s35 Formulation of government policy.

Whichever clause turns out to have been invoked, we will need to understand why some parts of the papers were considered to require censorship while others, often from the same paper, were not. My suspicion would be that Parliamentary privilege is the culprit. We know that some of the papers were put together as briefing papers for Lord MacKenzie’s part in the Lords debate on flat tax. It may be that the parts censored relate to the parts of the briefing he left out of his speech in the debate — that is to say the parts which didn’t support his case. This might explain why the excisions seem to have been almost entirely those parts supporting the concept of flat taxes.

Parliamentary Privilege would be intersting, because it would require a certificate signed by either the Speaker of the House of Commons or the Clerk of the Parliament. That’s certainly possible given the assertion by Nicholas Macpherson’ assertion that “no minister” was involved.

But what’s Parliamentary privilege, anyway? The Information Commissioner’s guidance on this exemption (PDF) says that this exemption is most likely to be used to avoid infringing its right to control the publication of its proceedings.

My guess, though, is that it will turn out to be a Section 35, “the formulation or development of government policy”. This is similar to section 36 in that it is ostensibly about providing ministers with a breathing space for receiving “free and frank advice”. This was what the Treasury spokesperson suggested was the justification for the redactions.

It doesn’t require a conclusive certificate from a minister, but would be interesting for other another reason: Unlike s34 or s36, Section 35 is a qualified exemption. This means that the government would have to weigh the public interest in disclosure against the public interest in invoking the exemption. That reasoning would have to be disclosed.

(Fellow open government geeks will be interested to read the inevitable Information Commissioner’s Guidance on this exemption, too [PDF].)

The public interest test reasoning would have to explain why releasing the pro-flat tax information is exempt while the anti-flat tax information is not — which, as Bishop Hill points out, gets to the heart of what is odd about this case.

Although it’s not just clear whether or not it has happened in this instance, the use of the most controvertial exemptions of FOIA for political purposes is something everyone who cares about open government should oppose — whether or not they like the idea of flat taxes.

We should know more soon. The 20-day statutory deadline for my request is on 19 September. I hope to have an answer by then. If not, I will certainly be complaining to the Information Commissioner’s Office.