Controversial comedian Louis CK left Saturday Night Live viewers confused and uncomfortable after a lengthy joke about child molestation.

Opening the last episode of the 40th season, he mused that the life of a child sex offender is so horrific that abusing young boys 'must be really good'.

He compared the 'addiction' to his love of Mounds bars, saying he would reluctantly give them up if he knew they could land him in jail for life - 'but they obviously don't taste as good as little boys'.

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Controversial: Louis CK opened SNL with a controversial joke about what makes sex offenders abuse children

Confusion: Twitter users expressed confusion as the comedian compared abuse to his love of Mound bars

The audience went quiet, the band behind him shook their heads, and it divided opinion on Twitter.

Laughing at the tense reaction, he then joked: 'That'll probably be the last joke I tell on this show'.

It came after a joke about 'mild racism' and another about the Middle East, in which he called Israel and Palestine 'selfish little bitches'.

One Twitter user wrote: 'SNL is making me feel strange and uncomfortable right now #confusion'.

Another said: 'Hoping victims of Child Molestation managed to miss the disgusting SNL monologue of #LouieCK #sodonewithim @nbcsnl #sexabusenotfunny.'

One wrote: 'Whole new level of bad taste.'

And another sent a tweet direct to NBC demanding an explanation, writing: 'Molestation/racism...REALLY...who on the staff gave the go ahead for THAT SNL monologue? Funny it was NOT! Offensive to many...yes!!!'

Author, professor and critic Dr Anthony Bradley, of New York's Kings College, wrote on Twitter: 'Sorry. Joking about child molestation is bad form. Very low moment for #LouisCK. 100% not funny in any form. 1 in 3 girls, 1 in 6 boys.'

He then tweeted NBC direct: 'Child molestation themed comedy with #LouisCK is a disappointing low. Would it be ok to joke about women being raped? Why kids?'

However, others applauded the joke, which is typical of Louis CK's controversial comedy.

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One wrote: 'Louis CK should do every #SNL monologue from here on out. Whether he's hosting or not. That is if they let him do it again after tonight.'

And another said: 'If you thought that monologue was "over the line" I feel sorry for you ----get out more #SNL'

Louis CK has hosted SNL three times since 2012, and has been widely well-received.

Among the comedian's high profile sketches is one that confronts the taboo of 'The N Word' - in which he says 'n*****' and 'c***'.

True to form, his turn hosting Saturday Night Live was saturated with jokes about race and politics.