The figures come from a survey by the Money Advice Service (MAS). If those who cannot get into debt, under 18 except for a student loan, are taken out of the population then nine million becomes a huge percentage. In some places more than 40% of the population are in this position.
What the report does not tell us is what constitutes these debts. Some of them might be mortgages or student loans, but we have no real idea. What is hinted at, though, is that moat of these debts are for the 'luxuries' people want rather than need.
It is frightening, and it looks as though it will only get worse.