One in six adults in the UK, or 8.2m people, are struggling with debt worries and living with "problem" debt, according to a new study from the Money Advice Service and market analysis company CACI.
The councils with the most indebted residents in the UK are Sandwell in the West Midlands, Blaenau Gwent and Merthyr Tydfil, both in Wales, where the proportion was over 24 per cent compared to the UK average of over 16.1 per cent.
The London boroughs of Newham, Barking and Dagenham and Tower Hamlets also all featured in the top 10, at fourth, sixth and eighth place respectively.
On the other hand, East Renfrewshire and East Dunbartonshire, both in Scotland, and East Dorset were found to be the local authorities with the least indebted adults.
Adults aged 25-34 were the group most likely to be living with a debt problem, with one in four - or around 2.1m - of them struggling.
The study found that the likelihood of developing debt problems peaks at this age, but doesn't begin to fall significantly until 55-64.
Renters and families, especially single parent families and those with three or more children, were also more likely to be affected.
Renters were twice as likely to be over-indebted than house owners, at 25 per cent and 12 per cent respectively, while having children increased the probability of debt problems by more than 50 per cent.
The report studied the characteristics of around 16,000 people, taking into account age, tenancy, income and household make-up, to identify where the most over-indebted adults live across the UK.