Many women secretly keep savings accounts without their partners' knowledge in an attempt to give themselves extra financial security, research published yesterday showed.
A report by the Fawcett Society, which campaigns for sex equality, found that most women interviewed tended to keep a "secret shoebox under the bed" while others covertly opened bank accounts.
The study, Home Truths, was based on the annual British Household Panel survey, which questioned 10,000 in 1999, and interviews with focus groups of women aged 25 to 35 and 55 to 65.
The majority of those who earned less than their partners said they kept the funds as a form of personal pension because pensions had been overlooked in the family budget.
Geethika Jayatilaka, who co-wrote the report, said the research showed the modern image of an egalitarian family was a myth.
"People can often find it harder to talk about money in relationships than sex. When they do, they often assume that families share money fairly but it is clear from this that this does not always happen," she said.
The report found that men controlled spending, especially in families where women had a low personal income.
Twenty-five per cent of women with incomes below £400 a month said their partners had the final say in financial matters, compared with 20 per cent of women with higher earnings.
Ms Jayatilaka said: "Because men earn more than women they have greater control of how money is spent or shared, and more access to personal spending. Bringing money into the household brings with it a sense of entitlement to decide how it is spent."