The director of Oxfam's operations in Haiti has resigned amid an inquiry into allegations of misconduct by staff.
The UK-based aid agency said Roland Van Hauwermeiren felt he needed to resign as he had been in charge at the time.
A small number of Oxfam workers in Haiti have been suspended, pending the outcome of an inquiry, it added.
The charity raised $98m (£60m) for relief operations after last year's massive earthquake but Oxfam said the allegations were not linked to fraud.
Oxfam has used the money to try to improve sanitation in the face of a cholera outbreak, said to have killed almost 6,000 people and made 420,000 ill.
The staff suspended are not thought to be British nationals.
Under Mr Van Hauwermeiren's direction, Oxfam was one of the few international aid agencies to openly criticise relief efforts.
On the anniversary of the quake in January, it said in a report that "the Haitian state, together with the international community, [was] making little progress in reconstruction".
"Too many donors from rich countries have pursued their own aid priorities and have not effectively co-ordinated amongst themselves or worked with the Haitian government," Mr Van Hauwermeiren said at the time.
Oxfam has been working in Haiti, the poorest country in the Americas, since 1978.