Donald Trump has accidentally posted a picture of killers Fred and Rosemary West on his Twitter account after being targeted by a troll.

Trump retweeted a message that had been sent to him by @feckhead saying: "My parents who passed away said you were a big inspiration. Can you please retweet (the message and image) for their memory?"

The tweet included a picture of the Wests, which Trump retweeted to his 2.7m followers.

Twitter users were quick to pick up on the billionaire businessman's mistake, with Tom Eldridge tweeting: "Social media 101 lessons for Donald Trump. I would do some research before posting."

Fred West, who murdered at least 12 women between 1967 and 1987, killed himself in 1995 while awaiting trial. His wife Rosemary, who took part in most of the killings, is currently serving a life sentence.

@feckhead describes himself on his Twitter profile as a 'drinker and failed comedian'.

The original tweet from @feckhead:

Hi @realDonaldTrump. My parents who passed away always said you were big inspiration.Can you pls RT for their memory? pic.twitter.com/veBxFNXnOd

And Donald Trump's response on Twitter after realising his mistake: