Despite sales of 3.8 million for Adele’s album “21” — the biggest single-year tally ever in the U.K. — and record singles sales, the BPI reported an overall decline of 5.6% in British album sales during 2011.

The U.K. music trade org tied the drop to rampant piracy.

Biz’s loss came despite a 26.6% increase in digital album sales to 26.6 million units; 15 albums sold more than 100,000 digital copies. Sales of digital singles climbed 10.4% to 26.6 million units.

However, CD album sales slid 12.6% to 86.2 million units.

The CD remained the principal format in the U.K., accounting for 76.1% of sales, vs. 23.5% for digital and 0.3% for vinyl. The latter format boomed nonetheless, climbing 43.7% in 2011.

Adele single-handedly propped up music in her native country: Her chart-topping album was the year’s domestic bestseller, while her renascent 2008 debut “19” placed No. 4 among the year’s top titles. Her tunes “Someone Like You” and “Rolling in the Deep” placed first and ninth among the bestselling singles of the year.

Still, unrestrained piracy torched Blighty biz, according to BPI chief executive Geoff Taylor.

“British artists continue to produce incredible music that resonates at home and around the world,” Taylor said in a statement. “But while other countries take positive steps to protect their creative sector, our government is taking too long to act on piracy. … Unless decisive action is taken in 2012, investment in music could fall again — a creative crunch that will destroy jobs and mean the next Adele may not get her chance to shine on the world stage.”

Nielsen SoundScan is scheduled to release year-end figures for the U.S. on Wednesday.