Watch: Trump's embarrassing gaffe, asks to look into 'oranges' of Mueller investigation

Donald Trump has found himself the laughing stock of social media after he struggled to say the word "origins", instead, repeatedly coming out with the word "oranges".

The US President was addressing reports at a briefing with NATO General-Secretary General Stoltenburg over findings of the Mueller investigation.

When asked about the Mueller report, Trump said: "I hope that this investigation now, which is finished – it's totally finished, no collusion, no obstruction – I hope they now go and take a look at the oranges, the oranges of the investigation."

Feeling the need to clarify he continued: "the oranges of the… uh… investigation, the beginnings of that investigation".

"You look at the origin of the investigation, where it started, how it started, who started it, whether it's McCabe or Comey or a lot of them.

"Where does it go, how high up in the White House did it go? You will all get Pulitzer Prizes, ok? You'll all get Pulitzer Prizes. You should have looked at it a long time ago and that's the only thing that's disappointing to me about the Mueller report.

"The Mueller report I wished covered the oranges, how it started, the beginnings of the investigation, how it started. It didn't cover that, and for some reason none of that was discussed."

Trump repeatedly fails in attempt to say 'origins' then claims noise from wind farms causes cancer. Photo / Getty

Trump has also been called out after he lied to media about his father's origins.

At another point in the meeting, Trump claimed his father Fred Trump was born in "a very nice part of Germany", when in fact his father was born in New York.

"I have great respect for Angela and I have great respect for the country," said Trump. "My father is German, was German, born in a very wonderful place in Germany so I have a very great feeling for Germany."

Trump's grandfather, Friedrich Trump, was born in the German village of Kallstadt.

Later on Tuesday evening, at a National Republican Congressional Committee event, Trump untruthfully stated wind turbines cause cancer.

"If you have a windmill anywhere near your house, congratulations, your house just went down 75 per cent in value," Trump told his audience. "And they say the noise causes cancer. You tell me that one, OK? Rerrrr rerrrr!"

For years before he became president, Trump falsely claimed former president Barack Obama was born in Kenya, a conspiracy theory he repeated even after it was disproved.