Pope Francis the most widely read on Twitter thanks to retweets

Pope Francis has by far the most clout of any world leader on Twitter because he is so widely retweeted, a study of political use of the social network shows.

With 14 million followers for the nine different language versions of his Pontifex account, the cyber-savvy pontiff boasts just a third of those notched up by US President Barack Obama.

But that it not the key measure, said Matthias Luefkens, who steers the annual Twiplomacy survey.

"It's not the number of followers which is really important, but the reach, the engagement," he said.

The real benchmark is tweets retweeted by followers to their own network.

Pope Francis wins hands down, with his Spanish-language tweets retweeted more than 10,000 times on average, and his English-language tweets 6,400 times.

Obama's 2012 election victory tweet - a photograph of him embracing First Lady Michelle Obama and the words "Four more years" - was retweeted a massive 806,066 times.

But on average, Obama gets 1,400 retweets.

Obama's use of social media is credited as a key factor in his landmark 2008 election.

The BarackObama account, created in 2007, has 43.7 million followers, but is not a US presidential feed and is run by his political campaign staff.

The official White House account has more than 4.9 million followers, putting it fifth in the global pecking order, just behind India's new prime minister, Narendra Modi, and Indonesia's President Susilo Bambang Yudhoyono, who has five million.

The White House was narrowly overtaken on Wednesday by Modi. "Modi's seen a stratospheric rise," Luefkens said.

Luefkens is a social media expert at communications firm Burson-Marsteller, which produces the Twiplomacy study.

He said while television remained the key channel to hit the widest audience, Twitter was an increasingly powerful tool. "It helps you to broadcast, and if you broadcast to the right audience, that has huge impact," he said.

Twitter is also a tool for leaders to follow one another mutually - a statement in itself.

French Foreign Minister Laurent Fabius follows 91 peers and world leaders, who return the favour, putting him at the top of the Twiplomacy mutual connections table.