Shoppers need to improve their maths skills to avoid "crippling" debts from credit deals offered by stores at Christmas, a government agency says.
Shoppers are surrounded by temptations to spend at Christmas
It is estimated that more than a third of Britons will spend more than their budget this Christmas and a further quarter will set no budget at all.
The Learndirect agency, which offers flexible learning courses, said poor maths skills meant "excess pressure".
The UK's consumer debt passed £1 trillion for the first time this year.
Learndirect spokeswoman Sue Densley said: "The Christmas period puts a lot of
excess pressure on the family purse strings and it's no wonder that a massive
proportion of people end up over-spending and dealing with the burden of
enormous debts once January arrives.
"Loans, interest rates and financial incentives can be very difficult to understand and it's clear that lots of people are signing themselves up for financial help around Christmas without really understanding how much it will cost them in the long run."
Financial illiteracy is a continuing problem in the UK, where total consumer debt passed the £1 trillion - or £1,000 billion - in the summer.
For the past three years, 300 secondary schools in England have been teaching personal finance issues such as managing credit.
A report from Brunel University said the scheme had proved to be an aid to awareness.
The Personal Finance Education Group wants lessons in all secondary schools, but says new funding is needed to extend its scheme.