More than 300,000 people contacted the StepChange Debt Charity between January and June - the highest half-year figure it has seen in records going back to 2011. People grappling with unmanageable debt owe on average £13,826 each with credit cards, overdrafts and personal loans the most common source of problems.
A total of 313,679 sought help from the charity during the first half of 2016.
The charity said its data suggests those affected by unmanageable debt are becoming more likely to be younger, working part-time and renting their home.
Almost 20 per cent of its total clients are now part-time workers, up from 16 per cent in 2011.
The charity has also warned that zero hours, part-time and temporary contracts are contributing to people’s financial vulnerability as a result of volatile incomes.
Mike O’Connor, chief executive of StepChange, said: “These figures paint a worrying picture of the reality of problem debt across the UK.”
The charity said rapid rent rises have also left people struggling.
Around 77 per cent of StepChange’s clients now rent homes, which has risen from 55 per cent in 2011.