Legislation put forward by Representative Ted Poe and Senator Rand Paul would remove the mandatory response requirement from all but four ACS questions – name, contact information, date of response and number of people living or staying at the same address.

The ACS replaced the Census long-form survey in 2005 and is sent to 3.5m US addresses every year, providing extensive data on demographics unavailable elsewhere, the MRA said.

It added: “The ACS provides the baseline for private and public sector survey, opinion and marketing research by ensuring the accuracy and proper weighting of statistical samples for the research profession.

“This is why the MRA will continue to advocate against [the legislation] and related efforts that would impair the ACS.”