Wells Fargo & Co. is seizing a bigger share of U.S. corporate bond sales, underwriting its highest portion of deals on record this year as the bank climbs the ranks after buying Wachovia Corp. in 2008.

Wells Fargo, the fourth-largest U.S. bank by assets, has underwritten 5 percent of this year's sales, excluding self-led deals, up from 3.6 percent in 2009, according to data compiled by Bloomberg. The bank has aided borrowers from Clorox Co. to Newfield Exploration Co. in sales of $48.3 billion, ranking it as the eighth most active underwriter of the debt. That's up from 11th in 2010.

The lender has sought to expand its investment banking business after acquiring much of the operation from Wachovia. An early target for expansion was debt underwriting, in units from investment-grade and high-yield corporate bonds to leveraged loans. The bank has built market share since the financial crisis, taking advantage of its large deposit base and limited presence in Europe.