Are Facebook friends with anyone who always seems to be causing trouble online? Do you resist unfollowing people - even really irritating people - for fear of causing offence?

If so, you are not alone. According to a new study by researchers at Nottingham Trent University, some Facebook users remain friends online with troublemakers because they are worried about the repercussions if they unfriend them.

Research lead Sarah Buglass, a PhD student in the School of Social Sciences at Nottingham Trent University, said: "People are spending more and more time online making them more vulnerable to potentially damaging social tension and disagreements.

"Our study explored the characteristics of people who might be more likely to cause this sort of trouble in an online social network."