The stats, based on Official Charts Company data, show that in Q2 2012, digital downloads accounted for 34.7% of all albums sold.
However, overall album sales in Q2, including physical formats, were down to 20.6m from 23.5m - a drop of 12.7% compared to the same quarter in 2011.
Digital album market volumes grew 15.0% in Q2 and 17.3% in the first half of the year.
The market for singles also continued to grow, with Q2 sales of 46.9m, up 8.3% year-on-year compared with 43.3m in 2011 and an increase of 6.3% year-to-date (93.6m, against 88.0m for H1 2011). Digital accounted for 100% of sales of the top 10 singles of 2012 so far.
Adele's 21 was the best selling artist album of the year so far in 2012, mirroring its performance as the biggest seller from the first half of 2011 a year ago. Our Version Of Events by Emeli Sande was the second-biggest artist seller of 2012, with Lana Del Rey's Born To Die at No.3.
The UK's biggest-selling single of 2012 so far is Somebody That I Used To Know by Gotye ft Kimbra - having sold more than a million copies. It is followed by Call Me Maybe by Carly Rae Jepsen and Titanium by David Guetta ft Sia in third place.
BPI Chief Executive Geoff Taylor said, "We've had another solid quarter of digital growth in sales volumes - both in albums and on singles, where the top 10 were exclusively sold as digital downloads. Album unit sales are down quite significantly year-on-year, but it's important to remember that these unit sales figures do not take into account the growing importance of music streaming and subscription services.
"The second half of 2012 is looking very promising for music fans, with big releases anticipated from The Killers, Plan B, Joss Stone, Mumford & Sons, Robbie Williams, Muse, David Guetta, Van Morrison, Pet Shop Boys, Dido, One Direction and The Vaccines."