US President Donald Trump's senior adviser Kellyanne Conway has come under fire after a picture of her casually kneeling on a couch in the Oval Office was widely shared on social media.

In an image captured by an AFP photographer, Conway appears on the couch with her shoes on as Trump poses for a photo with leaders of historically black colleges and universities.

Wall Street Journal columnist Bret Stephens was among those taking aim at Conway, suggesting that aides under previous administrations would have elicited even greater outcry.

"If Rice or Jarrett had sat like this in Oval Office, conservatives would have screamed themselves hoarse for weeks. Now we own trashy," he wrote, referring to previous presidential aides.

Trump's predecessor Barack Obama repeatedly took flak for photos in which he appeared to be relaxing.

Critics also chastised Obama for unbuttoning the previous Oval Office dress code that called for a suit jacket and a tie.

The image of Conway trended widely on social media, with several Twitter users berating her for what they described as a lack of respect in the Oval Office.

This is not the first time Conway has found herself at the centre of a storm.

She recently came under fire for plugging the fashion brand of the president's daughter. The head of the US Office of Government Ethics urged the White House to investigate Conway after the incident, saying she should face disciplinary action.

She also famously coined the term "alternative facts" and referred to a "Bowling Green massacre" -- which never happened -- during an interview.

Conway later tweeted that she meant to say "Bowling Green terrorists" -- referring to two Iraqi men who were indicted in 2011 for trying to send money and weapons to Al-Qaeda, and using improvised explosive devices against US soldiers in Iraq.