NEW YORK – A coalition of state attorneys general, as well as Colorado Gov. John Hickenlooper, on Monday urged the U.S. Department of Commerce to not add a question about citizenship to the 2020 census, saying it could lower participation among immigrants and cause a population undercount.

New York Attorney General Eric Schneiderman, Massachusetts Attorney General Maura Healey and California Attorney General Xavier Becerra led a letter sent to Commerce Secretary Wilbur Ross.

The letter said they were opposing a request by the U.S. Department of Justice to add the question, and that it would chill “participation in the 2020 census by noncitizens and naturalized citizens alike” over fears about confidentiality and possible data-sharing.

Diminished participation would be detrimental to states, the letter said, because it would impact a range of outcomes, from political representation in Congress to federal funding of programs used by the states.There was no immediate comment from the Commerce Department.

The U.S. Census Bureau is obligated to carry out an “actual enumeration,” the letter said.”Including a question on the 2020 Census that would manipulate the count by scaring people away from being counted – causing grave harm to the states and our residents – is inconsistent with those obligations,” the officials wrote.

They were joined by Connecticut, Delaware, the District of Columbia, Hawaii, Illinois, Iowa, Maine, Maryland, Mississippi, New Jersey, New Mexico, Oregon, Pennsylvania, Rhode Island, Vermont and Washington.