Working Families runs a free telephone legal helpline and receives about two calls a day from parents concerned about how they will cope without tax credits.
The organisation carried out a survey of employers representing a quarter of a million employees, to find out their likely responses when their employees ask for more hours of work.
It found two thirds of employers who responded are unaware of the changes to WTC rules and less than a fifth of employers (17%) are confident of accommodating a request for eight more hours of work.
A further 33% said they may be able to offer some hours, but not eight, while 17% said it was "unlikely" or "impossible" to accommodate a request.
When asked about the impact on business if an employee left because they couldn't get more hours of work, only 17% said "business would suffer". Fifty six per cent thought it would be a "minor inconvenience" and 17% were confident that they could easily recruit a replacement.
Only half of employers would create jobs of less than 16 hours a week if they thought there was demand for them from parents.
Working Families chief executive, Sarah Jackson (pictured), said:??"The change to the Working Tax Credit rules are harsh: parents will find that it is no longer worth staying in work. Many of our callers have one parent (often the mother) in a part time job, struggling to make ends meet after the other parent has been made redundant. It isn't for want of trying that these parents can't get more work: our survey shows employers can't offer them what they need to stay out of poverty.
"We call on the Government to reverse this change in the forthcoming budget. Until the economy picks up, making parents look for work that just isn't there and taking away tax credits is all stick and no carrot."
