The onetime speaker of the Pennsylvania House of Representatives pleaded guilty Wednesday to eight criminal charges stemming from a public corruption investigation, making him the highest-ranking state politician to be convicted in the four-and-a-half-year inquiry.

Ex-Rep. John M. Perzel entered the plea to two counts of conflict of interest, two counts of theft and four counts of conspiracy. He left the courthouse without commenting, but apologized in an e-mailed statement and said he bore responsibility for improprieties in spending public funds he controlled.

"It was up to me to see that taxpayer funds were spent only for the betterment of the people of Pennsylvania, and not for my political benefit (or) that of my party," Perzel said in the news release.

Prosecutors have described Perzel, 61, as being at the center of a scheme to spend millions of taxpayer dollars on computer technology for the benefit of GOP political campaigns.

Also Wednesday, his nephew and co-defendant Eric S. Ruth, 36, pleaded guilty to conspiracy and conflict of interest. Ruth once worked in the House Republican technology office.