There are more unmarried mothers in the prosperous Kent town of Tunbridge Wells than in the poor London borough of Tower Hamlets, a survey has shown.
Tunbridge couples felt marriage was an "unnecessary luxury"
It found 33% of babies were born outside marriage in Tunbridge Wells in 2002, and 21% in Tower Hamlets.
The study was compiled by the Economist magazine, based on figures from the Office of National Statistics.
Researchers said the countryside could no longer be seen as the bedrock of traditional family values.
In the Kent town, many unmarried couples have families together, while in inner London young people of south Asian origin are traditionally expected to be married.
In Tower Hamlets, the proportion of children born out of wedlock was lower than in the country as a whole and was falling, the survey found.
Childbirth outside marriage is low among groups including Bangladeshis, Pakistanis and black Africans, according to the research.
Dr Muhammad Abdul Hannan, director of Tower Hamlets Parents Centre, said marriage was a holy institution to the Bangladeshi culture and it was rare to find an unmarried Bangladeshi mother.
"The family structure is very important. There is a father who is the head of the family, most mothers are housewives and they have lots of children," he said.
"Young people brought up here are influenced by western modern culture. Even so, parents expect their sons and daughters to be married."
Almost half of Tower Hamlets' population were from ethnic minority groups and one-third was Bangladeshi, according to the 2001 Census.
This compares with Tunbridge Wells where white people made up almost 98% of the population.
Question of choice
In Tunbridge Wells, Rev Stuart Biggs, of St James Church agreed there had been a decline in marriage.
"In our society people have had more choices, so they choose not to get married rather than to choose to be married," he said.
"It has a knock-on effect with our community - a lot of communities are breaking down."
Social researchers found co-habiting couples felt marriage was no longer essential, but a luxury to splash out on when there was enough money for a big celebration, reported the Economist.