A study by the University and College Union (UCU) revealed a "tale of two Britains", with one in four people having no qualifications in some areas.
Cities across Britain are "blighted" by hotspots of educational under-achievement, with huge differences in the number of residents with qualifications, according to a new report.
Research in the 632 parliamentary constituencies in Wales, England and Scotland showed that Glasgow, Birmingham and Wolverhampton are among the areas with the highest number of residents with no qualifications.
But there are pockets of under-achievement within every region, said the union.
UCU general secretary Sally Hunt said: "This research shows that access to the benefits that education brings is heavily rationed in Britain today with some constituencies having almost 13 times more people without qualifications than others.
"It is unacceptable that there is such widespread under-achievement in Britain today. We live in a fast-changing knowledge economy where education is key to employment and getting on.
"It is this knowledge economy that will drive economic growth, enhance social mobility and enable our country to compete globally.
"Yet politicians all too often seem to see cutting off access to educational opportunities as an easy target. Given the opportunity, everyone can benefit from education."