It's easy to demonise labour agencies. The stereotype is straight out of a Guy Ritchie film: grubby back-street office, battered white van and dodgy-looking paperwork. Such outfits have no place in the world of integrated supply chains. But still, every contractor knows that if they need five brickies in the morning, these guys will dredge 'em up – from Albania, probably (pages 22-25).

Contractors are faced with a choice: stick with market forces or act in the long-term interests of safety and productivity by getting rid of the industry's dark underbelly. Their chance to do the latter will come at this month's DTI employment review, where the malpractices of certain agencies will be on the agenda, alongside the wider issues of the black economy and illegal immigration. It's an opportunity not to be missed. Most agencies are, of course, perfectly law-abiding. But if their reputation is vicariously tarnished by any crackdown, they'll only have themselves to blame. For years, both bona fide agencies and contractors have been turning a blind eye. But the game's up now. It has been up ever since Potters Bar.

Still, won't skills shortages keep the rogues in business? Perhaps. But the government's vast public building programme means we can at least be certain of what labour will be needed this decade. Forget seasonal immigration. But a regulated supply of skilled workers from overseas, plus retraining the long-term unemployed, would undermine contractors' reliance on the Lock Stock brigade. As for them, the police might follow its recent raid on illegal immigrants at Paternoster Square by blitzing other flagship sites. And laws against tax-dodging scams – such as "composite companies" – would also prove that ministers are serious. With Gordon Brown fretting about dwindling tax revenues, how can he ignore the £1-2bn that disappears in construction each year?

Construction – by which we mean everyone from clients to specialists - must also play its part. Contractors ought to know who's working for them, whether they're staffers or freelancers. Is their National Insurance card genuine? Have they been trained? If not, don't give them a site pass. The industry doesn't really lack power to crack down on rogue agencies – just willpower.

Who's really to blame, John?
So, Two Jabs has become Two Jibes. At the urban summit, John Prescott made a dig at housebuilders for building too few homes, inefficiently and at too low a density (see pages 14-15). He also called for more off-site manufacture. Fair enough, but why blame housebuilders? As whizz-kid engineer Darren Richards points out, they do want prefabrication – it's the public that isn't so sure (pages 50-51). And as for high densities, fine – many housebuilders would be grateful to get planning consent for anything. They can't, because councils are paralysed by nimbyism and delays to the planning white paper. The culprit Prescott really ought to be fingering is himself; but he is no Estelle Morris. Prescott prefers a fall guy and who better than rich, greedy housebuilders? But as Roger Humber argues, they are the very people Prescott needs to put a roof over nurses' heads (page 33). Let's hope he agrees to meet the House Builders Federation and they kiss and make up. The housebuilders should bring their gumshields, though – just in case.