The Chilean government has been advised to annul the latest census, taken in 2012, because it failed to account for nearly 10% of the population.
An independent panel said census takers failed to count more than one million people because they were not at home or homes were wrongly labelled as empty.
The panel recommends holding another census with fewer questions in 2015.
President Sebastian Pinera has been meeting government advisers to decide whether to accept their advice.
"The commission believes that the 2012 census suffers from serious problems,'' the experts said in their report, commissioned by the National Statistics Institute.
The commission said the government surveyed 15.8 million people, when it should have been closer to 17.4 million.
The commission blamed the problems on President Pinera's government but also said that problems during the administration of former President Michelle Bachelet delayed the census.
The 2012 census cost about $32m (£20m), according to Mariana Alcerreca, a former senior officer at the statistics institute.