Centrelink says more than 8600 reports of customer aggression towards its staff last financial year is an improvement, but its main workplace union says the welfare agency is hiding the extent of the problem.

The agency's bosses insist the workplace safety situation is improving but the union says plummeting customer service standards are driving high levels of verbal and physical aggression towards frontline Centrelink workers.

The CPSU alleges there is a deliberate drive to normalise threatening or aggressive behaviour in Department of Human Services workplaces so that incidents are not reported and that the "robo-debt" crisis is going to put more workers into the danger-zone.

It points to a survey of its members last year that reported more than 60 per cent of them had been the victims of aggression and says these finding are sharply at odds with the official figures.