(Adds details on Gross, fund)
NEW YORK, May 30 (Reuters) - Billionaire Bill Gross' bond fund dropped more than 3 percent in one day - its worst single-day performance since launching in 2014 - and plunged to last in its peer category, Lipper data showed on Wednesday.
Gross' $2.1 billion Janus Henderson Global Unconstrained Bond Fund is now down 6 percent so far this year after its showing on Tuesday, sending the fund to the bottom of the Alternative Credit Focus Funds category, according to data provided by research service Lipper.
Gross' underperformance came as bond market volatility surged on Italian political concerns. The yield on the benchmark 10-year Treasury note broke below 2.8 percent on Tuesday, as investors scrambled for shelter from potential eurozone contagion. When bond prices rise, their yields fall.
While investors typically judge fund performance over long time periods, the one-day losses mostly wiped out the gains Gross has produced for the fund's investors since he joined in 2014. Low-cost institutional shares are up just 0.13 percent since he joined, while most higher-cost shares of the fund are now negative, according to research service Morningstar Inc.
Calls and emails to Janus Henderson were not returned.
Gross, once considered the "Bond King" of Wall Street, co-founded Newport Beach, California-based Pacific Investment Management Co (Pimco) in 1971 but left abruptly in 2014 after a management rift and moved over to Janus. Gross is worth $2.5 billion, according to Forbes magazine.
Gross has been outspoken about his bearishness on U.S. government bonds and other sovereign debt.
In January, Gross told Bloomberg News that he had gone short - betting against - U.S. Treasuries as well as German and UK bonds. In a follow-up investment outlook note, Gross said the Treasury market has begun a bear market, though "not a dangerous one" for investors.
In March, he said he expected 10-year Treasury yields to rise to 3 percent - they did earlier this month - and stay there. But yields have fallen since then.
Gross again reiterated his stance in another investment outlook note in March that bond markets were like "a hibernating bear awakening" from a bull market driven by "lower inflation and excessive central bank accommodation."
U.S. 10-year yields dropped to seven-week lows of 2.759 percent on Tuesday before rebounding to 2.842 percent on Wednesday afternoon. Tuesday's drop was the largest since June 2016, helping Treasuries to their best day in more than seven years.
Todd Rosenbluth, director of mutual fund research at New York-based CFRA Research, said investors look to bond funds for capital preservation and income generation. The fund's marketing materials describe Gross as targeting "positive absolute returns in a variety of market environments."
"When a fund fails to deliver it can catch investors off guard," Rosenbluth said. "When Gross left Pimco assets failed to follow him. Unrewarded risk-taking fails to result in inflows." (Reporting By Jennifer Ablan and Trevor Hunnicutt Editing by Susan Thomas and Nick Zieminski)