But our use of plastic has not come with better financial planning and the professor of marketing at the University of Sydney's Business School, Paul Henry, warns that buyers will face nasty shocks when bills start arriving.

He said the best advice for people who spent too much in the pre- and post-Christmas sales was to stop using their credit cards.

''Cease using the credit card and work out a time period to pay it back so that you can pay it back as quickly as possible,'' Professor Henry said.

He said Australians needed to be educated about the real cost of credit, especially in the area of minimum repayments.

''More people are rolling over their debt each month and never pay off the entire amount.''

On a debt of $1000, with a standard 2 per cent minimum repayment allowed by credit card companies it would take about seven years and nine months to pay off the loan. On top of the $1000 loan the borrower would pay $859 in interest.

Professor Henry said impulse buying was a problem for many people during the holidays.

''All the social group pressure of buying presents, the display of giving, stops people from thinking too hard,'' he said.

''People need to make a conscious decision to allocate funds to pay off the credit card each week.''

Australians were expected to spend about $8.5 billion on Christmas presents, according to a RateCity survey that found adults planned to spend $511 on average during the holiday period. More than half of the 1000 people surveyed said they were going to pay for their gifts using credit cards. Of those, 81 per cent said they would pay off the balance during the interest-free period.

But 11 per cent said they intended to make just the minimum repayment while 6 per cent said they would roll over their debt.

Professor Henry said it was that 6 per cent who would end up paying almost double for their Christmas shopping.