In a document filed to the White House’s Office of Management and Budget, the Census Bureau said it expected that around 0.5% of the estimated population would not complete the census if the citizenship question is included.

However, the Bureau said it has "identified no credible quantitative evidence that the addition of a citizenship question would impact the net undercount of the 2020 census", CNN first reported.

The follow-up costs and additional workload created by non-response – mailings and in-person visits – "would be easily accommodated" in its agreed budget, the Bureau said in the statement.

The document said commerce secretary Wilbur Ross had "consulted extensively with the Census Bureau and a broad array of stakeholders" including "more than 24 diverse, well-informed, and interested parties representing a broad range of views". He and his staff reviewed "more than 50 incoming letters from stakeholders, interest groups, Members of Congress, and state and local officials" regarding the reinstatement of the question, it noted.

The decision to reinstate a citizenship question in the 2020 census was announced in 2018, but critics are concerned that it would negatively impact turnout in areas with large immigrant populations.

Around 99% of over 137,000 comments submitted as part of a public consultation on the issue were against the addition of a question on citizenship.

The US Supreme Court has agreed to hear a lawsuit over whether the question can be added, with a decision expected in June.