But, the British journal said, "the aid sector [is] undoubtedly an industry in its own right" and, unpalatable as it might seem, scrutiny of motives and performance was justified.
The editorial comes amid accusations by some countries and aid organisations that their relief planes were turned away - some repeatedly - from the sole Haiti airport receiving supplies.
Critics said the US military, in charge of operations at the Port-au-Prince airport since the quake, appeared to give priority to rescue equipment and military troops rather than humanitarian relief to help survivors.
But the US said it had prioritised flights according to the Haitian government's stated priorities.
"Large aid agencies and humanitarian organisations are often highly competitive with each other," The Lancet said.
"Polluted by the internal power politics and unsavoury characteristics seen in many big corporations, large aid agencies can be obsessed with raising money through their own appeal efforts.
"Media coverage as an end in itself is too often an aim of their activities. Marketing and branding have too high a profile.
"Perhaps worse of all, relief efforts in the field are sometimes competitive with little collaboration between agencies, including smaller, grass-roots charities that may have better networks in affected countries and so are well placed to immediately implement disaster relief."