Alan Wells, the unit's director, said: "There will be no 'quick fix' or 'magic bullet' to deal with a problem of long standing."
The report coincided with the outcome of the Government's review of the unit which recommended it should remain independent and widen its remit to work with under-16s. The review options included closure, merger or being managed by the Further Education Funding Council.
ALBSU's report, Older and Younger - the basic skills of different age groups, is based on a Gallup survey taken last year. Some 3,000 adults were asked to assess whether they had difficulties with literacy and numeracy; if so, what were the nature of these problems and their effect on their lives. Most were then given assessment tasks.
Fewer people in the oldest group, 70-72, said they had any difficulties with basic skills, but they performed the worst on average. But Mr Wells pointed out that this could be more due to the effects of ageing rather than improved standards.
It also seemed likely that there had been a decline in the numeracy skills of the 22 to 24-year-olds, the youngest group surveyed, he said.
The survey found that overall, 17 per cent said they had difficulties with reading, writingspelling andor numeracy. Writing and spelling posed a bigger problem - 13 per cent of the sample - than reading and numeracy at 4 per cent.
Those over 52 had more difficulties with the assessment tasks than those aged 44 and below. The best performance came from the 32-34 and the 42-44 age groups. Women did worse than men overall.
Older and Younger, free from ALBSU, Commonwealth House, 1-19 New Oxford Street, London WC1A 1NU.