Sean Spicer stands by Donald Trump in Jimmy Kimmel appearance

Donald Trump's former press secretary Sean Spicer has opened up on his time in the role, saying the President's tweeting "kept me constantly on my toes".

Appearing on ABC's Jimmy Kimmel Live on Wednesday night (local time), Mr Spicer revealed he'd had many a late night thanks to his employer's looseness on social media.

"There were times when you might have wanted to go to bed and you thought, 'Okay, this is going to be a little longer night'," he said.

"But that was one of the President's most effective tools on the campaign trail and he continues to utilise it, so you were constantly kept on your toes."

However he says despite Mr Trump's constant communication on the internet, it was reporters that were loosest with the information and responsible for the creation of 'fake news'.

"What I found frustrating was there were a lot of times when they were literally creating a story out of whole cloth that didn't exist.

"[Journalists] go on Twitter, and start to perpetuate myths and have back-and-forth," he said, before being cut off by an incredulous Kimmel.

"Hold on a minute: the journalists go on Twitter and perpetuate myths? What about the President?"

Kimmel also challenged Mr Spicer on the lengths he'd go to defend the President - with the ex-media man implying he would lie on his behalf, even if he didn't agree with what he said.

"Your job is to give him advice - he would always listen to that advice, but ultimately he's the President," Mr Spicer said.

"He's the President, he decides, and that's what you sign up to do."

In the wide-ranging interview, Mr Spicer also addressed speculation that President Trump 's work ethic, Melissa McCarthy's portrayal of him for Saturday Night Live, and the chaos of his first day in the job.