A quarter of credit cardholders said they had started 2008 more dependent on credit than they were last year, and 41% said they would be relying on their plastic to meet day-to-day living costs such as groceries, the Post Office said.

Gary Fitton, director of lending at the Post Office, said: "Many people have over-stretched themselves over the Christmas period and have little choice but to use their credit card in the New Year."

At the same time research from financial website MoneyExpert.com found that an estimated 6.9 million household bills were either paid late or went unpaid during the past six months.

Around 5% of people admitted they had either missed a council tax payment or paid it late, while 3% had struggled to pay a gas or electricity bill and 2% had not been able to afford their telephone bill.

Sean Gardner, chief executive of MoneyExpert.com, said: "For some time we have been waiting to see how the financial squeeze would affect the average household.

"Nearly seven million unpaid household bills is a fairly conclusive sign that we are feeling the effects."

But despite the strain people's finances are coming under, half of credit cardholders said they planned to use their card to buy something in the January sales and 28% said they would use it for a big purchase such as a holiday.

However, 53% of those questioned admitted they were unable to repay their credit card bill in full each month, the Post Office found.

Opinium Research questioned 2,004 people during December for the Post Office and YouGov questioned 2,082 people during December for MoneyExpert.com