Desjardins Group has booked an additional $220 million writedown on asset-backed commercial paper, nearly doubling its ABCP-related charges to $493 million.

The country’s largest credit union, based in Lévis, Que., said yesterday the first-quarter writedown reduced surplus earnings before member dividends to $67 million.

The $220 million writedown represents 11.1% of Desjardins’ $1.66 billion in ABCP holdings. Excluding the writedown, surplus earnings would have been $217 million, which was still an 18.1% drop from the same period a year ago.

Return on equity fell to 2.4% from 12.4%, but would have been 9.2% if the ABCP writedown is excluded.

Before yesterday’s announcement, Desjardins had taken ABCP-related writedowns of $116 million in the fourth quarter of 2007 and $157 million in the third quarter of 2007.

Total revenue fell 8.1% to $2.17 billion in the quarter.