Last year, 3.3 million young adults in the U.K. between the ages of 20 and 34 were living with a parent or parents, according to new data from Office for National Statistics.
That's 26% of the age group. As a comparison, 2.7 million lived at home in 1996, marking a 25% increase.
As the FT notes, the figure further highlights the "pressure faced by a younger generation hit by increasing housing costs and a difficult jobs market." London in particular has seen sky-high real estate prices in recent months, driven in large part by foreign buyers.
From the ONS:

ONS
The report also found that young men were more likely to live at home than young women.
And for those living at home, the unemployment rate was more than double than those who don't.
ONS