This is despite the number of people in this age group being largely the same in 1997 and 2011.
The figures from the Office for National Statistics show at age 20, 64% of men and 46% of women were living with their parents in 2011.
This decreases steadily until around the age of 30, after which the percentages remain more stable.
By the age of 34, only 7% of men and 2% of women were living with their parents.
The increase in the number of young adults living with parents over the past decade coincides with an increase in the average house price paid by first-time buyers, which rose by 40% between 2002 and 2011.
In addition the increasing ratio of house prices to the incomes of first-time buyers is well documented.
Nicholas Ayre, director of Home Fusion, says: “A 20% rise in the number of 20 to 34 year-olds living with their parents says all you need to know about the property market and economy – they’re broken.
“Property ownership is a pipe dream for the majority of today’s young adults while rents are at astronomical levels.”
He says renting was once the default option for people who were saving to own their own homes but now it’s a luxury.
He adds: “For a huge number of today’s young people, the only option, quite clearly, is to live with their parents.
“The root cause of this problem is a lack of supply. There just aren’t enough properties for people to live in.
“Both the current and previous governments said they would address this pressing issue, but neither has done so.
“We have policies that tinker around the edges rather than get to the heart of the matter.
“With the economy in a coma, lenders beating a retreat and the Eurozone threatening to unravel, it looks like the number of young adults living with their parents will continue to rise in the years ahead.”