StepChange Debt Charity said that a "toxic mix" of failing relationships and the continued tough economy are contributing to the rise, with problem payday loan debt also a growing issue.
Just over 1,000 single dads contacted the charity for help in 2007, rising to almost 4,500 last year. The charity, which released the findings ahead of Father's Day this Sunday, said that single fathers are making up an increasing proportion of its caseload, while the share of single mothers it deals with has remained fairly consistent.
The average amount owed by single fathers contacting StepChange is £17,549. They are also becoming more likely to be struggling with payday loan debt, owing £1,624 typically, the charity said.
Almost three in 10 (29%) single fathers seeking the charity's help said that a relationship breakdown was the reason for their debt problems, while one fifth (20%) put their difficulties down to redundancy or unemployment.
He said: "Parenthood, while wonderful, can be challenging financially. This is particularly the case when you are a single parent during an economic downturn.
"It is crucial that any single fathers who are worried about their finances and debt don't bury their head in the sand, but seek help as soon as they realise they have a problem."