In the 1970s, four out of five women got married under the age of 25, but now only one in ten women is married by the age of 25; a two-thirds reduction.
Fiona Banes, executive director of Time for Marriage, believes modern living has made getting married more unattainable.
Speaking on Premier's News Hour, she said: "The barrier of actually getting married is too high. The average cost of a wedding now is £24,000, and people just don't have that kind of money to spend, so they decide they'll live together for a bit, wait and see whether if they can afford to get married or whether it's the right thing to do."
"We've also had some quite bad examples set...The 40s generation is getting divorced quite readily and [younger couples] probably want to wait and see before they launch into [marriage] and commit to it."
Census figures also reveal that less than a third of women aged under 25 get married in a church now, and that the average age for a bride is 34.
Fiona Banes, Time for Marriage: