The survey found that one in three couples saw buying a home with their partner as a way to remove the pressure of having to get married, or at least allow them to delay tying the knot.
Over half of the respondents either have already, or would consider buying a property with their partner before getting married.
42 per cent of 18 to 34-year-olds in the survey said the main reason they would buy with a partner before marriage was because a joint mortgage was the only way they could afford to get onto the property ladder.
The Post Office findings also showed that people are increasingly also joining forces with friends and family as well as with partners to buy property. Some 44% of those not in relationships said they would get a mortgage this way.
Post Office Head of Mortgages, Mike Cook, said "Purchasing a property, whether it's with a partner or a friend, is of course a big commitment. With many first time buyers finding it hard to get on the property ladder, for some couples buying a house together before marriage is out of financial necessity, rather than just 'playing house'.
"We are also seeing an increasing number of applications from friends or family members buying together as people seek other ways to get themselves on the housing ladder. You can have up to four people on a mortgage, so friends can take that first step together."
As you might expect, the survey revealed a generational shift in attitudes to property and marriage. While 66% of over-55s thought marriage to be the greater of the two commitments, only half of under 34s felt the same and only one in five people are still taking the traditional approach of only considering buying a property once married.