The state attorneys general for Maryland and Washington, D.C. plan to sue U.S. President Donald Trump over allegations he violated anti-corruption clauses in the Constitution, the Washington Post reported late Sunday.

The lawsuit, potentially historically unique, focuses on payments and benefits to Trump's businesses from foreign governments and the president's failure to keep promises to separate public and private business, the report said. The Constitution's emoluments clause prohibits presidents from accepting payments from foreign governments.

D.C. Attorney General Karl A. Racine and Maryland Attorney General Brian Frosh, both Democrats, told the Washington Post that if a federal judge allows the lawsuit to proceed, one of their first steps would be to demand copies of Trump's personal tax returns to see the extent of his foreign business ties, the report said.

The D.C. Attorney General's office told CNBC via email that more details would be provided at a press conference at noon Eastern time on Monday.

The Maryland Attorney General's office and a representative of the White House didn't immediately return CNBC's emailed requests for comment, which were sent outside of office hours.

The Washington Post article can be read here.

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