Older people, mostly women, are giving up paid work to care for grandchildren so that their daughters and daughters-in-law can return to the labour force.

This intergenerational trade-off is identified in a new National Seniors Productive Ageing Centre report, Grandparent childcare and labour market participation, by Myra Hamilton and Bridget Jenkins from the UNSW Social Policy Research Centre.

Complementing a survey of 209 grandparents with focus groups, the researchers found 70 per cent had altered the days or shifts they worked; 55 per cent had reduced their working hours; and 18 per cent had changed jobs. In a separate question a third (33%) had changed the timing of their retirement to care for grandkids.

The disturbing finding, says National Seniors CEO Michael O'Neill, is that this role grandparents play in propping up the childcare system barely rates a mention in public policy discourse.

"Just as broken work patterns impact the super balances of younger women, so too they will affect the retirement savings of women who are leaving the workforce early to care for grandkids," he said.

"The extent to which grandparents are providing day care has significant policy implications beyond early childhood education to mature age participation and retirement incomes".

"Yet grandparents are barely mentioned in the Productivity Commission's final report into childcare; are excluded from the Coalition's in-home nanny-pilot; and currently receive no direct government support".

On a human level, O'Neill said the report confirmed the simple motivations behind caring for grandchildren.

"Older Australians are stepping in to reduce cost of living pressures on their adult children, but, ultimately, they just love spending time with their grandkids".

"Financial, lifestyle and health costs such as exhaustion from taking on more than 13 hours of care a week are seen simply as par for the course".

Pushed to identify support areas, grandparents nominated: community playgroups; flexible work arrangements; government compensation for care; and concessions on public transport or the movies to defray costs.

"Other developed countries are already recognising the contribution grandparents make to their economic and social fabric - its time Australia followed suit," O'Neill said.

In 2014, 837,000 children were cared for by grandparents in a typical week (ABS), this is far more than any other form of day care.