The group revealed the fall as part of its annual results, with the group also announcing a £732m underwritten rights issue.
3i highlighted recent investment buyouts such as Bestinvest as the main factor behind the soaring rise in loan impairments, with the firm unveiling a total of £848m in 2009, compared to £38m in 2008. Impairments to loans as a result of earnings based valuations were £620m.
Bestinvest has undergone a huge turnover of staff since its purchase by 3i in 2007 for an undisclosed sum.
Bestinvest refused to comment.