Annual growth in consumer credit hit 6.6% last month, the British Bankers' Association (BBA) said, despite weaker sales in the shops than in November.
The BBA, which represents the major High Street banks, said this was driven by demand for cheap personal loans.
The Bank of England has vowed to keep an eye on personal debt levels.
In November, Bank of England governor Mark Carney said: "We are going to remain vigilant around the issue, because we have seen this shift."
The net increase in consumer credit was Â£330m in December, the BBA figures show.
However, the BBA said that uncertainty regarding the economic and political climate in 2017 could lead to consumers having a more safety-first approach.
"Overall, we've seen high levels of consumer and business borrowing, although there are early indications that 2017 could see softer demand for credit from business and households, as they anticipate future interest rate rises and wait for further clarity on Brexit," said Rebecca Harding, the BBA's chief economist.
Analysts at Capital Economics said recently that there was no need to panic over household debts.
The cost of servicing debts compared to household income was still low and manageable, it said. Interest rates would have to rise significantly to raise this cost to the levels seen in 2008.
Separate figures from the Council of Mortgage Lenders estimated that gross mortgage lending reached Â£20.4bn in December.
This is 4% lower than November and 4% higher than December 2015. It brought the estimated total for the year to Â£246bn, a 12% increase on the previous year and the highest annual gross lending figure since 2008.
Borrowing on credit cards, loans and overdrafts rose in December, figures from banks show, amid concern over personal debt levels.