OTTAWA - The UN's special rapporteur for food is irking the federal government by calling on Ottawa to do something about the 800,000 households in Canada that can't be sure of their next meal.

The rapporteur, Olivier De Schutter, has just wrapped up an official trip to investigate hunger and poor diet across Canada.

He says he has severe concerns about the ability of families on social assistance and aboriginal peoples to afford a balanced diet.

He is also struck by the high rates of obesity linked to poor diet, which costs the public health system dearly.

But Immigration Minister Jason Kenney says the United Nations is wasting time and money and undermining its own reputation by sending someone to investigate one of the wealthiest countries in the world while people are starving in developing nations.