If Pope Francis was Donald Trump's presidential opponent, what sort of political vitriol would he receive?

A war of words between the Pope and the US Republican presidential candidate sparked the #MakeTheVaticanGreatAgain hashtag, after the pontiff called Mr Trump's Christianity into question.

The hashtag is a reimagining of Mr Trump's Make America Great Again campaign slogan.

Loading

The pontiff told journalists "anyone, whoever he is, who only wants to build walls and not bridges is not a Christian", when asked about Mr Trump's anti-immigrant stance.

The billionaire businessman and former reality TV star, who vows to build a wall on the US-Mexican border to keep out immigrants, called the Pope's comments "disgraceful" and said he was proud to be a Christian.

The comments and hashtag quickly became the top trending topic on Twitter in the United States.

"He wasn't even born in Vatican City, how can he be Pope? I'm just saying we should be looking into this #MakeTheVaticanGreatAgain," Travon Free tweeted.

Loading

Dan Scavino, Mr Trump's social media director, pointed out on Twitter the Vatican itself was "surrounded by massive walls".

While some supported Mr Scavino, other Twitter users quickly replied back saying the walls had "massive openings in them".

"Those walls are hundreds of years old and have massive openings in them," Twitter user Patrick wrote.

The Late Show, hosted by comedian Stephen Colbert, tweeted a Twitter poll in which it asked: "How can Donald Trump get back in the Pope's good graces?". The options listed were: "Cabinet position", "Purchase indulgences", "Evict Protestants" and "Sensual back rub".

Mr Trump, long the leader in national opinion polls, and five rivals face off on Saturday in South Carolina's Republican primary.

While the Pope and Mr Trump are now at odds, the business tycoon had previously praised the pontiff.

In 2013, the year Pope Francis began his papacy, Mr Trump compared himself to the Pope favourably.

On Christmas Day 2013 Mr Trump tweete: "The new Pope is a humble man, very much like me, which probably explains why I like him so much!"