A 72-year-old Washington lawyer who represents oil companies before the Federal Power Commission pleaded guilty in U.S. court here yesterday to evading nearly $16,000 in federal income taxes in 1972.

The lawyer, Charles E. McGee, overstated his charitable contributions by $12,188, understated his interest and dividend income by $14,803 and over stated his business travel expenses by $3,573, Assistant U.S. Attorney Stephen R. Spivack told U.S. District Court Judge Thomas A. Flannery.

As a result, the prosecutor said that McGee, a founder of the law firm of McGee and Ketcham, actually ahd taxable income of $101,104 in 1972, not the $73,171 he reported to the Internal Revenue Service.

Sprivack said that McGee claimed in the 1972 return that he made contributions to 70 groups, but that actually did not make the donations to some of the groups or gave less than he said he did. The prosecutor said that McGee filed similar claims for 1970, 1971 and 1973 and had an extra $54,000 in undeclared taxable income for those years.

Paul Machalek, the IRS agent who investigated the case, said after McGee pleaded guilty taht the IRS has sent him a civil tax claim for $177,521, including penalties, for the four years.

MeGee told a reporter that he regretted "the mistakes that were made. I was doing my own taxes then. I don't know anything about tax law. Some of these (figures) were estimates.

"It's not really that much. It's only $16,000," McGee said of the tax owed for 1972.

McGee faces up to a five-year prison term and a $10,000 fine. Flannery scheduled sentencing for June 21.