Nagin has said he made the appeal to former residents planning to move back to help city secure government funding, which is partly determined through population as revealed via the U.S. Census.
But Gabriel Sanchez, director of the Census Bureau's regional office in Dallas, which oversees Louisiana, Mississippi and Texas, told Saturday's Times-Picayune that advice goes against the rules and practical limitations of the census.
"The residency rule is what it's been since 1790," said Sanchez. "We need to count people where they live, not where they plan to live or where they want to live."
There are no spaces on this year's short census form for respondents to fill in an address other than the one where they're living now, the New Orleans newspaper said.
Sanchez told The Times-Picayune that while his agency "does not prosecute people" for lying on their questionnaires, "putting things that are not true on your form" could produce a follow-up visit by a Census Bureau employee or cause the form to be thrown out.