Image caption Three-quarters of adults said it was harder to raise children if their mothers worked, the survey found

Mothers are increasingly the primary breadwinners in their families, a new report has found, marking a dramatic shift in US household finances.

A record 40% of US homes with children relied on mothers as their main or only source of income, a Pew survey found.

Of the women supporting their families, 37% were married women who earned more than their husbands, while 63% were single mothers, the report said.

In the 1960s, just 11% of families were supported primarily by mothers.

According to the Pew report, married women with a higher income than their husbands tended to be older, white and college-educated.

They were likely to earn much more than single mothers, who on average tended to be younger, more likely to be black or Hispanic, and less likely to have attended an institution of higher education.

For married women, the median total family income was almost $80,000 (£53,000) compared to the median income of $23,000 for the families of single mothers.

In the US about one-quarter of all households are headed by a single mother and women make up nearly half the national workforce.

According to the study, which was based on census data, the employment rate among married women rose from 37% in 1968 to 65% in 2011.

Working mothers 'divisive'

The authors of the Pew Research Center report said it was unclear if the financial crisis had an effect on the trends.

But the study noted that since 2007, more women have said they wanted to work full time and fewer said they would prefer not to work at all.

The study also said that women's growing role in the workforce remained divisive.

While women in the workforce bring clear financial benefits to their families, the study said three-quarters of adults said it was harder to raise children if their mothers worked, and half said it was harder for marriage to succeed under those circumstances.

Yet most Americans do not believe women should return to a traditional role in the home.