One in eight people surveyed for the charity said they are likely to see their finances slip back in January as a result of their Christmas spending.
This equates to six million people falling behind financially if the findings among more than 2,000 people are projected across Britain.
Despite the relatively large number of people who expect to struggle, just one in 100 said they are “very likely” to ask for help with managing their money and tackling their debts.
The charity, which runs the National Debtline, fears that many households will leave it too late and see their financial position deteriorate further in the new year.
Joanna Elson, chief executive of the Money Advice Trust, said: “Our New Year message is simple. If you are dreading the arrival of that first credit card bill in a couple of weeks, now is the time to act.
“Set a budget by working out how much you have coming in and how much you need to spend each month, and open all of your statements to get a handle on how much you owe.”
Here are the National Debtline’s top three suggested financial resolutions for the New Year:
1. Set a budget for 2015. Sit down and work out how much money you have coming in every month, and what you need to spend. Do not forget to account for annual expenditure, like car insurance or road tax, by dividing it through by 12.
2. Open all of your statements. Ignoring the problem will only make it worse, so take a deep breath, open all of your statements and get a handle on how much you owe. Write down a list of all of your debts, together with the outstanding balances and repayment dates for each.
3. Seek free advice early. The earlier you seek free advice, the quicker and easier your problem will be to solve.