The former head of the Office of Government Ethics bashed “corrupt” politicians, lobbying groups and foreign governments using President Donald Trump’s Washington hotel to “funnel cash” to the president.

Walter Shaub, who served as ethics chief under presidents Barack Obama and Trump, spoke up Saturday after Rep. Ted Lieu (D-Calif.) posted a letter on Twitter turning down an invitation to a gala last month hosted by Kuwait at the Trump International Hotel.

“Regrettably, it was held at Trump International Hotel DC,” Lieu noted in his tweet. “Potus’ continued ownership of this hotel raises serious ethical/legal questions (see Emoluments Clause of U.S. Constitution). Therefore, we declined.”

The hotel, located in a landmark building owned by taxpayers and leased by the Trump Organization, is at the center of a lawsuit arguing that the business violates the Constitutional prohibition against a federal official accepting payments or gifts from states or foreign governments — like those that book rooms and events there. Shaub and other ethics experts say the hotel is also an easy conduit for cash from anyone hoping to curry favor with the president.

Shaub praised Lieu’s rejection of the invitation, and accused members of Congress who attended the bash of “complicity in the only ethics violation our founders sought to prevent.” He said lawmakers have a “constitutional duty to conduct meaningful oversight of the executive.”