WASHINGTON — Former acting Attorney General Sally Yates, speaking publicly for the first time about concerns she brought to the Trump White House on Russia, told Congress on Monday she warned that National Security Adviser Michael Flynn “essentially could be blackmailed” because he apparently had lied to his bosses about his contacts with the Russian ambassador.

The statements from Yates, an Obama administration holdover, offered by far the most detailed account of the chain of events that led to Flynn’s ouster from government in the first weeks of the Trump administration.

Yates, appearing before a Senate panel investigating Russian interference in the 2016 presidential election, described discussions with Trump White House Counsel Don McGahn in late January in which she warned that Flynn apparently had misled the administration about his communications with Sergey Kislyak, the Russian ambassador.

White House officials had insisted that Flynn had not discussed U.S.-imposed sanctions with Kislyak during the presidential transition period, but asked Flynn to resign after news reports indicated he had misled them about the nature of the calls.