We remain perplexed, readers, by the apparent total lack of interest in the mainstream Scottish media about how many members the Scottish Labour “party” has.

Membership levels are a topical subject in the light of the extraordinary explosion in SNP and Green membership after the referendum, and with a general election just months away in which the make-up of Westminster’s 59-strong Scottish contingent could be crucial to the shape of UK politics for the next five years.

The number of members the main Unionist party north of the border can call on to knock doors and deliver leaflets will therefore be a very significant factor in the outcome. Yet on this morning’s Sunday Politics, when presented with an ideal and pertinent opportunity to question new Scottish “leader” Jim Murphy on the subject, Gordon Brewer didn’t even try to ask. What’s with that?

One possible explanation is that we’ve been told on social media – though haven’t yet managed to verify it – that the state broadcaster’s reporters James Cook and Glenn Campbell both claimed this weekend to have been informed that Labour has 14,000 members in Scotland, a number in excess of any estimate of the last five years.

(Lazy journalists often trot out a number of 13,000 which is erroneously based on a 2010 Caledonian Mercury article revealing that the party sent out 13,135 ballot papers in Scotland for the election of Ed Miliband. But that figure ignores the fact that ballot papers don’t equal membership – under Labour rules a single member can have as many as four, five or six votes, if they’re Parliamentarians and/or a member of trade unions – so we know membership must have been below that figure.)

That doesn’t square with an article in Friday’s New Statesman – a publication very close to Labour – which said the party “is believed to have no more than 10,000” members. That’s an estimate it also made five weeks ago, saying on 6 November that “the SNP now has more than 80,000 members, compared with less than 10,000 for Labour north of the border”, and had it been in error one imagines Labour would have been on the phone correcting it before now.

A few weeks earlier the Evening Times had been even more specific, citing “Sources in the party” who suggested membership “could be as low as 8000”. The figures in the two publications would be around the same ballpark as this site’s own crude guess of closer to 5000 last year, based on analysis of published membership income figures in Labour’s accounts.

But it wasn’t until a reader pointed us to another article that we looked at the Caledonian Mercury piece again, and this time a little lightbulb appeared above our head. The CalMerc story noted that Labour had been claiming 20,000 despite only sending out 13,000 ballot papers, and the discrepancy was accounted for by the presence of 7000 social-club members.

These are people who join “Labour” clubs – essentially pubs with function rooms – in towns across Scotland for the cheap beer and social events, but who aren’t actual members of the party and have no voting rights. If we assume that their numbers would be unlikely to be significantly affected by political developments (you don’t stop liking a pint just because you disagree with transport infrastructure policy), it would be reasonable to imagine that most of those 7000 were still there.

If we then include them in the “14,000” figure that Labour are apparently giving to journalists now, suddenly all the numbers start to make sense. If roughly 7000 of those are non-voting social-club members, that leaves 7000 “real” members – a figure which fits with the ones in the New Statesman, Evening Times and our own analysis.

It would also explain why Labour still refuses to release actual voting numbers for its membership elections, because admitting to having fewer paid-up political members than the Scottish Greens (8000) would be a crushing embarrassment.

(We can’t think of another election of any kind anywhere in Britain where the voting percentages are released but not the actual number of votes. It’s an extraordinary degree of secrecy, particularly as while refusing to publish member and trade-unionist figures Scottish Labour HAS revealed not only the numbers of Parliamentarians who voted in the three-section electoral college, but also the full individual details of who each MP, MSP and MEP voted for.)

It’s dismaying that if BBC journalists have been reporting the “14,000” claim [EDIT 1.37pm: They have] they haven’t sought to clarify such points. But for the first time it looks like we finally have a plausible explanation for the vast discrepancy between the oft-reported 13,000 figure and the revenue in the accounts which suggests far fewer.

If Scottish Labour has 7000 “real” members and 7000 social-club ones, all the data and the quotes in Labour-sympathetic publications back each other up. Everything works. The numbers fit, the income fits, and the embarrassed secrecy fits. Unless we hear anything from Labour to the contrary, we’re filing this one under “case closed”.