Robert Downey Jr has warned fans of an online scam in which individuals are attempting to impersonate him.

The Iron Man star told followers on his official Twitter account to be vigilant of people “claiming to be me” and asking for money.

He said: “I will never communicate via private chat platforms, and I would never ask individual fans for money for any reason.”

Downey Jr said any message from him will always come through his verified social media accounts and “all fundraising is done via broad, public campaigns”.

He added: “I am constantly humbled by the incredible love, support and generosity of our little community. Some want to take advantage of that, so let’s have each other’s back.”