You love your best friend and you've been close for years. Then they become romantically involved with someone - and you take an instant dislike to their new partner.

You try to give them the benefit of the doubt; after all, your friend sees something in them. But the more you see, the less you like. You don't want anything to affect your friendship, so what do you do? Ask yourself the following questions:

• Does the new partner treat your friend well?

If you're concerned your friend has embarked on a destructive relationship, you must act. Give it time and then gently explain your concerns. Reiterate that you think the world of them and that they deserve the best, and to be loved by the best. Then, sit back and wait to see if the seed you planted germinates. Take a mental note of examples of poor treatment and slowly point them out.

But always remind your friend that you're a friend for life and will be there for them, no matter what happens or who they love.

• Has your friend changed since the relationship?

Most of us are guilty of changing to some extent to impress a new partner, so it's not surprising if your friend behaves a bit differently. Give them time. Hopefully the changes will be short-lived and the real friend will re-emerge soon.

• How close are you?

It's possible that your friend's new partner is uncomfortable around you because your friendship is so close. It's often a good idea to see what this person is like in his or her own circle - how they act when they're with their friends and family.

• Are you just not spending the same amount of time together?

We all try not to do it, but a new relationship can take precedence over friendships. It can be hard to wait in the wings, but before long you'll be right back in the picture.

• Is your friend happy?

If you're a true friend, a loved one's happiness will be very important to you. They won't be very happy, though, if their best friend doesn't get on with their partner. As long as the relationship isn't destructive, you need to be supportive.

By all means, initiate activities for just the two of you, or in a group but without including partners. As time goes by, you'll probably be seeing the partner less often, but early on you might just have to grin and bear it.

A true friendship needs to be treasured and nurtured. You'll know it's solid if it can handle the influence of an unlikeable partner or two along the way.

For more great life advice from Jo Lamble, check out the latest issue of New Idea - on sale now!