As someone who believes that the private sector tends to be, overall, more efficient and productive than the public sector, I was eating a lot of humble pie last week.

I regularly defend the private sector, and even from time to time celebrate it. Now I was deeply embarrassed. The shaming incompetence of the company G4S – which does a great deal of sensitive and lucrative security work for the Government – in failing to provide thousands of temporary security staff for the Olympics, as it was contracted to do, was nothing less than a humiliating debacle, a disaster that exposed the private sector as both inefficient and untrustworthy.

G4S had, many months earlier, agreed to provide 10,000 short-term staff; but with just days to go before the Olympics, it transpired that they simply could not do what they had contracted to do. For the wider private sector, this was a public relations calamity.

Looking for something, anything, to retrieve from this disaster, all I could find in extenuation was that G4S immediately agreed to pay in full for the 3000 or so soldiers who had to step into the gaping hole left by the company's failure. Not that this really changed the underlying reality, for the soldiers coming, as so often, to the rescue of the British state are themselves very much part of the public sector.

The armed forces – themselves facing draconian cuts when they are already grievously overstretched – stepped up to the plate when the private sector had gone missing. So I felt I had to rethink, to revise some of my beliefs or, some might say, prejudices. However this new mood did not last too long, for a familiar figure burst into the limelight, with consummate timing, to show the public sector at its abysmal worst, and enthusiastically reclaim the low ground. The man who stepped forward was that predictable bogeyman, Mark Serwotka, leader of the Public and Commercial Services Union.

Mr Serwotka announced that this coming Thursday, the day before the Olympics start, his members, who provide crucial security at the entry points to Britain, would walk out. The timing of this particular "action" looks nasty at best, downright malevolent at worst. There was predictable indignation, and not only from the Government. Mr Serwotka responded, a tad disingenuously, by claiming that what he termed "hysteria" about the effect on the Olympics was misplaced, because the 24-hour strike would be held the day before they started. This conveniently ignored the fact that many people arriving from abroad to attend the Olympics will be arriving in advance.

Mr Serwotka had some gall to make any announcements about the strike at all, given that it was called on such a pitifully flimsy mandate. Only 20% of those who could take part in the ballot bothered to do so. This lamentable turnout hardly indicated that the bulk of Mr Serwotka's members were desperate to flex their muscles. And of this 20%, only just over half – 57% –backed the call for strike action. So Thursday's walk-out was voted for by just over 10% of this particular electorate: not the most ringing endorsement in British industrial history.

Ed Miliband, the increasingly confident and impressive leader of the Labour Party, was quick to condemn the strike and demand that it be called off. I can think of many Labour leaders in the past who in similar circumstances would have equivocated or blustered. But whether Mr Serwotka will heed his comrade's sensible advice (and he still has time to do so) is of course another matter.

Mr Serwotka can be accused of arrogance and insularity, while his unfortunate intervention has deflected attention from the G4S shambles. And shambles it was; a large private sector organisation contracted to provide essential security for the most important public event in Britain in a very long time woefully failed to fulfil its obligation. The behaviour of Mr Serwotka and his members is a mere sideshow compared to that disaster.