A study has found that an increase in “diversity” makes existing residents of a area feel unhappier and more socially isolated, while those leaving for more homogenous areas populated by their own ethic group often get happier.

Among the reasons for residents feeling insecure as their area diversifies, is that people tend to spend time with those they perceive as like them, and feel less secure when experiencing rapid change, the authors explained.

Already around a fifth of people in the UK are non-white or non-British. This is expected to rise to a quarter by 2025, a third by 2040, and could reach up to 38 per cent by 2050.

The large-scale sociological study, undertaken by the Cathie Marsh Institute for Social Research at the University of Manchester, drew on 18 years of data of more than 10,000 people.

“With immigration at historically high levels across many European countries, research suggesting ethnic diversity negatively impacts social cohesion has engendered alarm”, begins the paper.

However, the report found little to dispel such concerns, as it purported to “demonstrate a negative association between community ethnic diversity and indicators of social cohesion (especially attitudes towards neighbours and the community), suggesting diversity causes a decline in social cohesion.”

The only group which appeared to be unaffected by diversity was those who willingly chose to move into such areas.

Sociologist Dr. James Laurence, who co-authored the study, said: “There has long been an ‘assumption’ increasing ethnic diversity in an area undermines residents’ social cohesion.

“On one hand our study supports this, for example where people report feeling happier when they move out of diverse areas and into neighbourhoods where they are surrounded by more people like them.

“However we find there are people happily moving into diverse areas who are unaffected by the presence of different ethnicities and social groups.

“Also diversity actually has a relatively weaker effect on people who stay in a community in which diversity is increasing around them.’

Speaking to the Daily Mail, he added: “Increasing diversity may reduce cohesion as people simply see their neighbours as being more different to them; that they may have different values, different interests and different norms, which can hold up contact.”