ANU research says one in three families will be worse off under the Federal Government's planned changes to child care.

The study undertaken at Australian National University (ANU) was funded by Early Childhood Australia. It will be presented as part of a Senate inquiry into the Jobs for Families package.

A Senate education committee is looking at the Government proposal to merge certain childcare subsidies combined with a new activity test.

Researchers used Australian Bureau of Statistics data to model both the existing scheme and one with the Government’s proposed changes.

While the experts predict more than 700,000 families will be better off or at least stay at the same level of Government support, but things would be worse for around 330,000 families.

“Of those, about 150,000 would lose as a result of the tighter activity test, so parents would now need to be working at least eight hours a fortnight to receive any subsidies, and many families don't,” Mr Phillips said.

Early Childhood Australia CEO Samantha Page says the activity test findings were particularly concerning.

“We are pleased that the majority of working families will be better off under this package but we are concerned about the high number of children that potentially will miss out altogether,” she told the ABC.

“The children that we are particularly concerned about, and the reason we commissioned this work in the first place, are the ones that are potentially pushed out of early learning because their families, for one reason or another, won't meet the activity test.

“It's really important that very young children, if they're going to attend early learning services, have a continuity of access and aren't in one minute and out the next.”

Early Childhood wants the planned package amended to make sure that families get at least two days of subsidised care a week before the activity test takes effect.

Education Minister Simon Birmingham acknowledged that the report showed the Government needs to collect better modelling data.

“The report says; ‘Commonwealth will have a superior data base with the full population of formal childcare families and exact price and hours information for child care use’,” he told reporters.

“And also points out; ‘The data in the survey however does not necessarily line up exactly with the legislated policy, as some people will be undertaking training or charity work that is not covered by the surveys’,” Minister Birmingham said.

“However our analysis can absolutely be trusted and is based on a ‘complete picture’ and actual outcomes that take all factors of the Jobs for Families package in calculation.”

Minister Birmingham claimed that almost one million families would be better off under Government analysis of data including exact hours, prices of child care use per child, and family with work activity.

“Our objective is to better help parents who want or need to work, or who want to work more, while still supporting early childhood education. More affordable access to quality child care puts the opportunity of work within reach for more families,” Senator Birmingham said.

Findings from the Senate Inquiry are due later this month.