21/10/2016 5:00 AM AEDT | Updated 23/10/2016 1:39 PM AEDT

How To Tell A Friend Really Bad News

Without them shooting the messenger

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He might be your best friend's boyfriend but what if you don't approve of him?

One of the biggest tests of any friendship is knowing when to keep quiet when you don't approve, or dislike, a friends' partner. It might be because they are not treating your friend well, or it might be because they outright annoy you.

Whatever the reason, only you can be the judge over whether you keep your mouth shut or let your friend know how you feel. But when it impacts on your friendship - perhaps you start to avoid your friend when you know their partner will be joining in - that might be the time to come clean.

When you can't stand your friend's partner

Psychologist Alison Hill told The Huffington Post Australia if you really dislike your friends' partner, you need to ask yourself why - and whether telling her is worth risking your friendship.

"If it's just a case of you find their partner irritating, perhaps he has an annoying laugh or doesn't laugh at all, then those are not reasons to risk alienating your friend. However if you have concerns or you see a change in your friends' behaviour, I would call that out," Hill said.

"Maybe your friend used to be very outgoing and now she has become a recluse, or she removes herself away from the friendship group. You should be able to recognise the warning signs when it comes to something serious. If you really think the relationship is having a negative impact on your friend, you need to talk to your friend."

"Maybe your friend was actively supporting a charity but their partner keeps putting them down or putting down her values. In these cases, you need to call them out. All you need to do is let her know you are concerned. But if you just find her partner annoying, you should keep quiet and remind yourself that your friend loves their partner."

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If you think telling your friend you don't like their partner will damage your friendship, you need to ask yourself why you need to tell her.

When you find out your friend's partner is doing something bad

Whether you discover your friend's partner is cheating, or is indulging in criminal activity or is doing something to jeopardise your friend's life: that's the time you need to speak up. But, first Alison Hill suggests you make sure your facts are correct.

"The reality is, it will be a very difficult conversation. Remember to put yourself in your friend's shoes. How would you feel if she was telling you the same thing? Make it clear that you are keeping her own best interests at heart and that you understand this is a very tough situation," Hill said.

"You need to be respectful, without 'beating around the bush.' Be prepared that your friend might not want to believe you at first. There is no easy way to have a conversation like this and much of it depends on how strong your friendship is, and how much your friend trusts you. Only you will know whether it is important for you to speak out, or stay silent."

Only you can be the judge of whether you need to tell your friend you dislike their partner. It could ruin your friendship.

When your friend breaks up with her partner & you say you hated him.

And then they get back together.

"You can't unsay what you already said," Hill said. "You need to deal with this right away or it will always be the elephant in the room. You can sit your friend down and tell her that there were things that bothered you at the time. But you need to be mindful to be respectful about their relationship."

"If you say nothing, you will cause a major rift. So it's best to say, 'As you know, I told you I didn't like your partner. But I want you to know I'm still here to support you in your relationship and I want you to be happy.'

"If there are things about her partner that still grate on you, you might need to keep quiet but you need to decide whether your friendship is more important and only you can be the judge of that."