Barclays Plc's $3 billion of new contingent capital notes, securities designed to ensure taxpayers aren't forced to pay for banks' errors, fell for a second day.

The 7.625 percent subordinated 10-year notes were priced at face value and have dropped 1.55 cents on the dollar to 98.45 since the sale closed two days ago, according to Jefferies International Ltd. The notes will be written down to zero if the U.K.'s second-largest lender has losses that reduce its core Tier 1 equity ratio to 7 percent or lower.

The securities were marketed globally and attracted orders of more than $17 billion, with most coming from Asia, Mark Harmer, the head of developed markets credit research at ING Groep NV in Amsterdam, said in a client note. Its size and relatively high price leaves it vulnerable to short sellers, according to Paul Smillie, a Singapore-based bank credit analyst for Threadneedle Asset Management.