Procurement policy on blacklisted construction workers?

Scottish construction workers protested on Friday about the discovery of a blacklist of 'trouble maker' employees'. I had previously discussed the blacklisting and asked why procurement should interfere if a potential employer opted to bypass 'trouble makers'.

However, what the protest has brought to light is that, when you scratch a little below the surface you find that the definition of a trouble maker, in this case, also relates to some who raised concerns about health and safety. That's a much more serious issue, as not raising concerns about health and safety could lead to liabilities, delays in project completion and serious injury or even death. Silencing the trouble maker in this case amounts to something similar to silencing NHS and other whistle-blowers. Yes, I think we all agree that whistle blowing policies are a good thing.

However, the protesters are calling for a ban on public sector contracts being awarded to firms that have used the blacklists. How on earth would that work? Would it be legal? How would you answer one of your political masters if you were asked to advise? How would you advise your Board if you were in a private sector organisation committed to responsible procurement?

I can't really see any scope for the public sector to avoid using those involved in the blacklisting as it is quite probable that a number of the issues just aren't relevant to the subject matter of the contract. Yet, I do think there is scope for every public sector organisation to consider within the selection criteria the need for a whistle blowers policy. Would that not be a more pragmatic way to solving the problem and yet avoiding the direct risks of related potential increased delivery costs through site closures, etc.. and duty of care?

What would your recommendation be?