Star Wars: The Last Jedi director Rian Johnson has explained why he decided to delete around 20,000 of his posts on Twitter, saying "if trolls scrutinizing it for ammunition is the new normal, this seems like a 'why not?' move".

There had been much speculation about Johnson's "move", which came days after Star Wars makers Disney fired Guardians of the Galaxy director James Gunn from the third film in the Marvel franchise after offensive messages he had posted to Twitter were unearthed.

Responding to a tweet, Johnson said he had received "no official directive at all".

"I don't think I've ever tweeted anything that bad," he continued.

"But it's nine years of stuff written largely off the cuff as ephemera, if trolls scrutinizing it for ammunition is the new normal, this seems like a 'why not?' move."

Johnson said such housekeeping could be done "literally with the flip of a switch".

Watch our interview with Rian Johnson from last December: