The presenter was praised for her opening to the show, in which she said Boris Johnson’s chief advisor “broke the rules” and added: “The country can see that, and it’s shocked the government cannot.”
The BBC said in a statement on Wednesday that staff had been “reminded of the guidelines” around impartiality following the broadcast.
In her opening to the programme, Ms Maitlis said: “The longer ministers and the prime minister tell us he worked within [the rules], the more angry the response to this scandal is likely to be.
“He was the man, remember, who always got the public mood, who tagged the lazy label of elite on those who disagreed. He should understand that public mood now – one of fury, contempt and anguish.”
In its response to the broadcast, the BBC said it must “uphold the highest standards of due impartiality in its news output”.
The statement added: “We’ve reviewed the entirety of last night’s Newsnight, including the opening section, and while we believe the programme contained fair, reasonable and rigorous journalism, we feel that we should have done more to make clear the introduction was a summary of the questions we would examine, with all the accompanying evidence, in the rest of the programme.
“As it was, we believe the introduction we broadcast did not meet our standards of due impartiality.”
Ms Maitlis was praised for the “brilliant” introduction to the show.
One person on Twitter said her comments were “most definitely needed,” while another tweeted: “Emily Maitlis has summed it up perfectly.”
Sharing a clip of the opening monologue, David Lammy, a Labour MP, called the Newsnight introduction “public service broadcasting”.
Last year, the BBC was caught up in an impartiality row over comments made by Naga Munchetty about Donald Trump and racism during a live broadcast.
The BBC Breakfast presenter was judged to have beached BBC editorial guidelines when she discussed remarks made by the US president after he told female Democrats to “go back” to their countries.
However, the ruling was later reviewed and reversed by the corporation’s director-general, Lord Tony Hall.
Earlier this month, Ms Munchetty said “lessons have been learned and things are improving after she had “very robust” conversations with senior figures at the broadcaster following the debacle.