The investigation is focussed on the speech he gave live from Jerusalem at the Republican National Convention.
Under the Hatch Act, federal employees are prohibited from engaging in any part of a political campaign while serving in government.
House Foreign Affairs chair Eliot Engel and House Appropriations chair Nita Lowey made the announcement in a press release on Monday, which also referenced Mr Pompeo’s role in releasing Hillary Clinton’s emails and his domestic campaign speeches.
“Our offices have confirmed that the Office of Special Counsel has launched a probe into potential Hatch Act violations tied to Secretary Pompeo’s speech to the Republican National Convention,” the two Democratic Party representatives said.
“This information comes on the heels of reporting that OSC is also looking into Secretary Pompeo’s stated commitment to rush out more of Hillary Clinton’s emails by Election Day and as the Secretary has misused State Department resources on his speech tour of swing states.”
Secretary Pompeo is accused of brazenly misusing the State Department and the taxpayer dollars that fund it as vehicles for the administration’s, and his own, political ambitions.
The department has repeatedly missed deadlines to produce documents relating to Mr Pompeo’s campaign speeches to establish if they were improper.
“We’re grateful to OSC — whom Mr Pompeo can’t fire as he did the Inspector General — for looking into this matter,” the statement continues.
It concludes: “Whether it’s before Secretary Pompeo’s departure or afterwards, the truth about this administration’s corruption will come out.”
In June 2019, the OSC found that White House special adviser Kellyanne Conway has repeatedly violated the Hatch Act, and recommended her removal from federal service.
No action was taken.