Many believe they will be provided for in later years. But the Carers National Association (CNA) fears they may be left in the lurch by "small changes carried out by stealth".
A poll commissioned by the charity shows only 4 in 10 people have given thought to who would care for them if they could no longer manage on their own.
Three out of four admit they have made no financial provision. And while most families are willing to care for their relatives, 6 out of 10 expect to receive some cash help from the state.
Less than half (47 per cent) say they would be willing to make compulsory extra payments towards the cost of caring for the frail or disabled.
One in four said he or she would be willing to make some voluntary payments, while the rest did not want to make any extra contribution.
The statistics, prepared for the CNA by Boots the Chemist, are based on an NOP poll of 902 non-carers.
It showed that women (53 per cent) are more likely than men (38 per cent) to have thought about what they would do if a relative needed care - and were more prepared to carry out tasks.
Nine out of 10 men and women would be prepared to do the shopping. However, 75 per cent of women would wash or bathe in their role as a carer against only 55 per cent of men.
The study follows the new Carers Act which took effect on 1 April and entitles carers to an assessment of their needs.
Jill Pitkeathley, chief executive of the CNA, said the survey highlighted the need for caring to be given a higher priority.
"People are not making provision for their future because they are acting on the premise that they will be provided for in old age.
"This is no longer the case. We must face the issue and be open about what we can and cannot afford.
"Otherwise we are heading for a serious crisis."Reuse content