Universities are being urged to design more courses to allow people of working age to get a degree.
There is a call for more part time study
Universities Secretary John Denham has told university leaders to attract more mature students by designing courses to fit in with people's lives.
Until now, the government has focused on getting more young people - aged from 18 to 30 - into university.
Leaders of the UK's universities support the move but say extra funding will be needed.
Mr Denham announced the drive in a speech to university leaders (Universities UK) in Leicester, saying courses should be based around the need of mature students to balance work, family and leisure with study.
"Two important trends are coming together which will inevitably have consequences for universities," he said.
"The first is that the rising tide of 18-year olds will begin to ebb, as UUK's own analysis this week shows. We estimate that population figures for 18 year olds in England will drop by just over 14% from 675,800 in 2006 to 579,300 in 2020.
"Secondly, as a country we simply cannot afford to have a higher education sector that is focused only on school and college leavers. As the Leitch report made clear, 70% of the workforce in 2020 has already left school. Many of them need university level education.
"Both trends will demand that you change your intake. We cannot meet the country's needs purely by educating the rising generation."
The report by Lord Leitch into the UK's skills needs last December called for more than 40% of adults to have degrees or higher level qualifications by 2020.
The qualifications should mostly be funded by employers or individuals, he said.
Leitch argues that employers should influence or even determine what universities offer, to ensure the UK has the skills it needs for the future.
John Denham supports that view and wants universities to work more closely with industry to provide part-time courses for their employees.
At the time of the Leitch report, Universities UK - which represents university leaders - described the target of getting 40% of adults to degree level or equivalent as "ambitious".
But the organisation said the goal recognised that lifelong learning and older learners would play an important part in achieving the highly skilled workforce needed if Britain was to remain a competitive global economy.
The courses would have to be paid for from extra funding streams, it stressed.
At the UUK conference, the group's president, Professor Rick Trainor, addressed the issue of increasing links between universities.
"We need to know more about the real needs of employers, but equally they need to know more about the types of education and training that universities are best equipped to provide," he said.
"They also need to understand the many ways in which teaching and learning in universities have changed for the better since employers, and vice-chancellors, were themselves students."