Parents who split before their children are six years old put youngsters at greater risk of being bullied, feeling lonely and being unhappy at school, a study suggests.

Danish researchers who analysed answers given by 219,000 children in the National Well-being Questionnaire, found that those whose parents separated when they were aged two to five had a greater changes of low social wellbeing than those aged six to 10.

Overall, one in 20 children (five per cent) were lonely, bullied, or struggled with school, but that rose by 41 per cent for those who came from dissolved families – the equivalent of an extra two children per 100.

And for those whose parents separated before the age of six the chance of unhappiness increased by 55 per cent, compared with 36 per cent for the six to 10s, and 30 per cent for the over 11s.