US President Donald Trump(L, front) and former US President Barack Obama. (Xinhua/Yin Bogu)

President Donald Trump's spokeswoman claimed Tuesday that Barack Obama staffers left behind catty notes in White House offices for the incoming administration, telling them "you will fail."

Press secretary Stephanie Grisham's comment, first made to a CNN reporter, prompted swift denials from ex-Obama officials and a torrent of online mockery from Trump opponents.

"We came into the WH, I'll tell you something. Every office was filled with Obama books and we had notes left behind that said 'you will fail,' 'you aren't going to make it,'" a tweet from CNN's Abby Phillip quoted Grisham as saying.

"This is a complete and utter lie," tweeted Obama administration lawyer Daniel Jacobson.

"Quite the opposite - we left them briefing books to try to help with the transition as much as possible," he said.

Jon Wolfsthal, a former senior director at Obama's National Security Council, called it "an outrageous lie.... Shameless and disgusting.@PressSec should be fired."

Faced by the heated denials - and snarky online gags about the "you will fail" prediction proving true - Grisham said her remark had been over-played."I don't know why everyone is so sensitive!" she told AFP.