People in the UK owe £55bn in hidden debts, according to a survey.
Nearly a third of people (31%) hide the true extent of debt from family members, according to the research by OnePoll for the Post Office.
One in six women (16%) and more than a quarter of men (28%) do not tell their partners how much they owe, the survey of 2,258 UK consumers suggests.
Although it is called personal debt, the family home could be at risk if a joint owner runs up huge bills.
Nigel (who has asked us not to use his full name), aged 69, who lives near Bath, was unaware his wife had taken out seven store and credit cards.
Over a few years the money she owed had spiralled to more than £50,000.
She had a good credit score partly because she jointly owned the family home. They have now had to take out a mortgage on their house to clear the debt.
Nigel said he believed the credit card companies acted irresponsibly.
"They were sending through pre-authorised cards to my wife. She had ticked a box stating that she was a homeowner but I was kept in the dark even though I jointly own the house with her," he said.
"The credit card companies should inform co-owners if their partners are running up huge debts, which could affect the family home.
"The debt does of course needs to be repaid. We have had to take out a mortgage on the house, which I can cover with my pension, but this was not how I hoped to be spending my retirement."
Credit card companies do not have to inform joint owners of an asset about debts run up by just one of the owners.
Although a co-owner of a property is not legally liable for their partner's personal debts, a lender can demand the equity the debtor owns. If the case goes to court and a charging order is granted, the property may have to be sold.
The British Bankers' Association (BBA) said ticking the "home owner" box on a loan application was part of the credit scoring process all lenders undertook.
"It has nothing to do with securing the loan and does not do so," said Lesley McLeod, from the BBA.
"If customers do not keep up payments, banks try to come with a mutually acceptable repayment plan.
"Only if that completely breaks down will they go to court to try to get the money back. It is during that process when assets are considered. Even then it would be a last resort to force a sale. More commonly the debt is covered when the house is sold voluntarily."
Chris Tapp, from debt advice charity Credit Action, said Nigel's position was unfair but not uncommon.
"You can find out if you are linked to another person's debt by running a credit check," he said.
"Re-mortgaging your home may not be the best option if you are in debt. A good debt management plan is an alternative. The most important thing is to speak to your lenders and seek independent advice from a debt advice charity."