More Australians than ever before intend to work beyond 70, as Generation X-ers and Baby Boomers fear they lack the financial security needed to retire any sooner.

The findings, which come as the Turnbull government weighs superannuation reform in the May budget, have sparked fresh concerns that a comfortable retirement is now "out of reach" for hundreds of thousands of low-income earners.

An analysis of Australian Bureau of Statistics data shows the number of over-45s who say they will not retire before turning 70 has dramatically increased, from 8 per cent to 23 per cent in a decade.

Seniors groups say the figures indicate people are ageing in a much healthier way and want to keep working, but also reveal deep "financial uncertainty" among older workers following a series of superannuation and pension changes.