According to an online audit of the prime minister's official Twitter account almost half his followers are considered fake.

While the tech-savvy leader has more followers than any other serving Australian politician – just over 654,000 – TwitterAudit has found 298,000 of them aren't real.

That leaves him with an authenticity score of just 54 per cent – the lowest of any senior federal politician.

While the audit result doesn't mean he has propped up his account with paid followers, it does mean he's done a poor job of purging his account of fakes.

It also means his one-time leadership rival Tony Abbott – who once dismissively described social media as "electronic graffiti" – actually has more real followers: 400,000 of his 615,000 followers are considered authentic.

In the lead-up to the 2013 election the Liberal Party was forced to deny it had paid to increase Mr Abbott's numbers after his followers suddenly spiked.

TwitterAudit takes a random sample of 5000 Twitter followers for a user to calculate its authenticity score.

It judges whether a follower is fake based on number and dates of tweets and the ratio of followers to friends.

"Of course this scoring method is not perfect but it is a good way to tell if someone with lots of followers is likely to have increased their follower count by inorganic, fraudulent, or dishonest means," its creators say.

While famous people and senior politicians always attract a lot of fakes, Mr Turnbull's ratio is particularly poor.

Politicians typically attract between 10 and 30 per cent fake followers.

Opposition Leader Bill Shorten has an authenticity score of 64 per cent among his 155,000 followers and Foreign Minister Julie Bishop 66 per cent among her 195,000-strong following.

Other leaders and frontbenchers score in the 70s or 80s: Barnaby Joyce (86 per cent); Chris Bowen (83 per cent); Scott Morrison (82 per cent); Anthony Albanese (82 per cent); Richard Di Natale (76 per cent); Tanya Plibersek (72 per cent); and Penny Wong (72 per cent).

Crossbench kingmakers Pauline Hanson and Nick Xenophon scored 89 per cent and 87 per cent respectively.

Former Labor prime ministers Kevin Rudd and Julia Gillard still have the strongest social media followings among Australian politicians, in a sign Twitter's political influence is waning. Mr Rudd has 1.66 million followers and an authenticity score of 64 per cent; Ms Gillard has 750,000 followers with a score of 60 per cent.

Fake followers have been an issue in the US Presidential campaign, with suspicion both Hillary Clinton and Donald Trump have purchased followers. Ms Clinton has a 63 per cent audit score to Mr Trump's 60 per cent.

Spambots follow prominent Twitter users to gain access to their audience in an effort to promote products such as porn sites.