PHILADELPHIA (Reuters) - Vice President Kamala Harris would adhere to President Joe Biden's vow not to raise taxes on middle-income taxpayers and has helped to determine the Biden-Harris' administration's approach to tax fairness, including higher taxes on the wealthy and corporations, U.S. Treasury Secretary Janet Yellen said on Tuesday.

"Vice President Harris has indicated her support for avoiding tax increases for middle-income families. So I believe that's a principle that she would adhere to," Yellen told an Internal Revenue Service event in Philadelphia with Pennsylvania Governor Josh Shapiro, a contender to be Harris' vice-presidential pick.

(Reporting by David Lawder; Editing by Mark Porter)