The public response to the news that two more groups of workers – Aslef train staff and UK Border Agency employees – are threatening to strike in the Olympic season inclines to weary resignation. That is understandable, but a more appropriate response would be indignation. While thousands will make their own contribution to the success of the Games as volunteers, and thousands of others have paid good money to attend as spectators, thousands more, encouraged by their trade unions, have exploited an opportunity to make an extra (hundred) bob or two. There is a word for this, and it is blackmail.

It all began when the RMT union secured bonuses for a variety of transport staff for working through the Olympics – that is, for doing the job they are paid to do. It continued when London Underground workers threatened to strike unless they were awarded an even bigger bonus than was on offer. There was then no stopping London bus workers, who secured their deal last week. Now we have 450 train drivers, whose antics could thwart the travel plans of those in Sheffield or Derby with tickets for the last few days of the Games, and border officials threatening to leave their posts on the day before the Opening Ceremony. The unions concerned deny they are exploiting the Games for their own selfish ends. That denial should be dismissed with the contempt it deserves.

Not, of course, that those more closely associated with the Games have set a particularly honourable example. The strong commercial emphasis at London 2012 and the lavish protections for sponsors send a message that is not lost elsewhere. The same goes for the bonus culture that still prevails in many other walks of life. There is, or has been, a go-getting climate, of which the Olympic bounty for transport and other workers represents just a tiny slice.

But this cynical little gold rush is unworthy. The Labour leader, Ed Miliband, is right to dissociate himself from it. It is the unacceptable face of trade unionism, and may well rebound in the shape of reductions in staff and investment down the line. The pity is that, either now or then, the working and travelling public will suffer, too.