The aggregate deficit of occupational pension funds covered by the U.K. Pension Protection Fund's 7800 index increased 20% to £266.3 billion ($402 billion) in December.
Total liabilities increased 3.4% in the month to £1.503 trillion, and total assets were up 0.3% over the same period, to £1.237 trillion.
The funding ratio decreased to 82.3% from 84.8% as of Nov. 30.
The index covers 6,057 funds. Of those funds, 81.5% had a deficit, and the remaining 18.5% had a surplus. That compared with 79% with a deficit, and 21% with a surplus as of Nov. 30.