HM Revenue and Customs has refused a Freedom of Information request to think tank the National Institute of Economic and Social Research (NIESR) on the basis that providing the data would affect ongoing negotiations with the EU on migrants' access to benefits.
NIESR requested data on how many National Insurance Numbers issued to recent migrants were "active", meaning how many showed recent payments of tax, national insurance or benefit claims.
HMRC said it had the data, but that it could not give it because it counted as "information held for the formulation or development of government policy". It said,
"As required by the Act, I have assessed the public interest for and against disclosure. There is a public interest in greater transparency which makes Government more accountable to the electorate and increase trust.
"However, following the General Election, there is an active negotiation process at an international level in which UK Ministers and officials are engaged to secure support from the European Commission and other Member States for changes in EU law governing EU migrants access to benefits in the UK, in line with the Governments manifesto commitments. The information is being used to inform the development of policy options as part of the negotiation process and therefore relates to the formulation of Government policy. HMRC continues to believe that releasing information in the form requested would, at this stage, be unhelpful to the negotiation process.
"Therefore in this case, HMRC is satisfied that the public interest in maintaining the exemption outweighs the public interest in disclosure."
NIESR argues that it has not asked for information relating to the policy proposals or negotations, and questioned how releasing this information would be harmful to the negotiation process.
Data like this belongs to the public, not the government. With immigration at such a high level of public interest and the impending EU referendum, it is particularly important that the public is able to rely on and access important information about migration.