Hilary Clinton argued during the presidential campaign that President Donald Trump could not be trusted with a Twitter account, let alone the codes to the US nuclear arsenal.

But after being inaugurated last week, Trump now has gained access to a weapon critics perceive as equally dangerous: the @POTUS Twitter account.

Trump's use of Twitter was seen as one of the reasons he managed to connect with vast swatches on the electorate last year.

His bellicose rants – fired off morning, day and night – were not to everyone's liking but revealed the thoughts of the man soon to become the leader of the free world.

Trump vowed at his inauguration ball to continue tweeting from the White House, but he could find himself with fewer followers after a mix-up saw millions of Twitter users accidentally follow the Trump-controlled @POTUS account.

The confusion came after Barack Obama relinquished control over the account. His POTUS account – including all of his tweets and followers – was archived as @POTUS44 [Obama was the 44th US president].

Twitter used scripts to transfer people following @POTUS44 to the new @POTUS account. However, the scripts went wrong and people who had stopped following the @POTUS account after it fell under Trump's control began following it again, without their consent – even when the unfollowed the account a second time, they were re-added.

Journalist Jordan Crucciola compared the switch to when iTunes accounts were given U2's new album without asking. "This is SO WEIRD. It's like U2's album on iTunes I DO NOT WANT IT," she tweeted.

Twitter founder Jack Dorsey apologised for the error. "This was a mistake, it wasn't right, we own it, and we apologise. No excuses."