Unfortunately National Insurance is not a contributory Pension scheme unless it has changed significantly since last time I checked.
Current pension and welfare costs (of all kinds) are supposed to be met by current contributions, which is fine if you have a significant young (and able to find gainful employment) populace to fund an insignificant number of short-living pensioners, as was the case when it was all set up. It works far less well when there is a declining proportion of the populace doing the funding, ever increasing life expectancy, and health costs which know no limits.
I don't have a solution, but am quite sure that forcing further slaves into the market place isn't one either. It will simply further erode the life-chances of marginally employable youngsters. Perhaps the hidden agenda is to reduce life-expectancy, thus slightly relieving the overall problem.