The secret to a happy married life? Never forgive your partner when they misbehave

It is meant to be the cornerstone of any strong relationship.

But new research shows that forgiveness is more likely to tear a marriage apart than keep it together.

Those not so easily forgiven were less likely to repeat their behaviour, due to a loved one's criticism and the feelings of guilt and loneliness they experienced.

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The findings, published in the Journal of Family Psychology, showed partners who got away with being moody, abusive or sarcastic to their spouses were much more likely to do it again.

Those that were rebuked or shunned were more inclined to curb their bad habits.

The research, by psychologists at the University of Tennessee, calls into question the long-held belief that forgiving a partner's minor transgressions is one of the building blocks of a solid relationship.

Dr James McNulty, from the university's department of psychology, recruited 135 newly-wed couples and asked each partner to keep a daily diary for one week.

In it, they recorded every time their new husband or wife engaged in 'negative' behaviour. This ranged from arguing and snapping to nagging and being moody.

They also had to record whether they forgave the transgressions, or instead strongly criticised their partner for their behaviour.

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Finally, each participant had to document whether, having been forgiven, their spouse continued to behave in a similar fashion the next day.

The results showed that forgiveness nearly doubled the chance of a husband or wife doing the same again the next day.

Dr McNulty said: 'Spouses were almost twice as likely to report that their partners had behaved negatively on days after they had forgiven them than on days after they hadn't.

'These findings demonstrate that forgiveness may sometimes harm relationships.

'There is one plausible explanation - forgiveness allows relatively negative partners to continue their negative behaviours, ultimately harming the relationship.'