Washington DC - The US federal tax agency has reached an agreement to share highly regulated taxpayer information with immigration authorities – a move that could help them identify immigrants they want to deport, court filings showed.

The deal is a victory for the Trump administration, which has launched a massive deportation push, but has caused an outcry by immigrant rights groups.

The Internal Revenue Service (IRS) allows millions of undocumented migrants to pay taxes, a move seen as boosting both their immigration cases and the financial health of massive US federal programs such as Social Security.

Taxpayer information such as home addresses, earnings, and family details are closely protected under federal law.

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But under the terms of the deal – which the court filing showed was struck Monday – Immigration and Customs Enforcement (ICE) can ask the IRS for information on people they are investigating or who have already been told to leave the country.

The court filing argued that the Department of Homeland Security, which oversees ICE, can "legally request information relating to individuals under criminal investigation, and the IRS must provide it."

It said that as of Monday no such information had yet been shared.

Immigration rights groups filed a suit last month to prevent the IRS from turning over data to ICE, US media reported.

The court filing from the government which revealed the deal was in response to that suit.

"If allowed to stand, this agreement will provide a roadmap for federal law enforcement to gain access to confidential taxpayer information without obtaining court order as required by law," Nandan Joshi, a lawyer for advocacy group Public Citizen, told CNN.