"In the past, it was always thought that if you improved the economic situation overall, if you invested in economic development, everyone would benefit and there was no need to target the poor," he said yesterday. "But this is not true."

His study compared the enrolment rates of 19- and 20-year-olds from the wealthiest 10 per cent of families with those with household incomes less than half the median level.

It found that in 2011, the enrolment rate among the richer group was 3.7 times greater than that among the poor. In 1991, the difference was only 1.2 times.

The study was based on the government's census figures from those years.

In 2011, 48.2 per cent of 19- and 20-year-olds from richer families were enrolled at universities, compared with 13 per cent from the lower income group, the study found.

That is a dramatic change from 1991, when the figures were 9.3 per cent and 8 per cent for rich and poor families, respectively.

While the number of university places had risen over the past 20 years, Chou said it had not eased the disparity. "Yes, you make the pie bigger, you increase the number of spaces, but it's the wealthy who benefit more," he said. "We need to help those in poverty so that their opportunities in education are not affected by their families' financial situations."

Professor Paul Yip Siu-fai, a public policy researcher with the University of Hong Kong, said better access to higher education in recent years had benefited society as a whole. Yet it was still easier for rich families to place their youngsters in university, via expensive international schools and other routes.

"The university penetration rate has increased overall," Yip said. "The system favours [richer families] - but probably not at the expense of the less well-off, because all groups have benefited."

Chou's study also found that youngsters living below the poverty line were more likely to pursue non-degree tertiary education - 30 per cent of them in 2011, versus 23.6 per cent for wealthier students. This was another indication that the best educational opportunities were more accessible to the rich, he said.

Yip urged the government to strengthen support for students, either financially or by other means, to prevent them from "going into debt" after graduating from sub-degree programmes, which were often privately run.

Chou called for more initiatives targeting young people from poor families, including scholarships and workable schemes for reducing tuition fees.

He recommended that the government allocate more resources to schools attended by larger numbers of children from poor households.

Equal access to education was "the most important vehicle for social mobility", but insufficient support for poor children might make it difficult to prevent intergenerational poverty, he said.

Efforts to define poverty should not only look at financial indicators, Chou said, but also at factors such as educational levels, so that support could be targeted at the needy. "This is to prevent people from losing out at the starting line," he said.