HARRISBURG -- Former state House Speaker John Perzel pleaded guilty to reduced charges this afternoon, making him the fifth and most high-profile of the corruption probe's defendants to cooperate with state prosecutors.

The former northeast Philadelphia lawmaker now faces penalties related to eight counts of conflict of interest, theft and conspiracy, a sharp reduction from the 82 counts with which he was initially charged.

His decision to no longer contest the charges is seen as a significant victory for the state attorney general's office, which alleges that Mr. Perzel masterminded a scheme centered around spending millions in public funds on computer software primarily used for House GOP campaigns.

Mr. Perzel, 61, had consistently proclaimed his innocence since being charged in December 2009. He made no comments about the case to reporters following the hearing, instead releasing a statement in which he apologized for his actions.

"The truth is that as the legislative leader of my caucus, I oversaw the spending of millions of dollars in taxpayer funds, and I bear the responsibility for the improprieties that occurred in the spending of those dollars," he said in the statement.

"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 of that of my party. ???You had a right to expect better from me, and I am sorry that I let you down."

While Mr. Perzel is cooperating with prosecutors as part of his plea agreement, he still stands to face prison time, a hefty fine and the loss of his remaining state pension.

The charges carry a maximum prison sentence of 24 years, plus a $50,000 fine, though officials said the minimum would be serving somewhere between 18 and 50 months.

In addition to Mr. Perzel, his nephew and former House GOP technology office employee Eric Ruth entered a guilty plea to one count each of conflict of interest and conspiracy.

Three other defendants in the case -- ex-Perzel chief of staff Paul Towhey, and Perzel aides Samuel "Buzz" Stokes and Don McClintock -- entered guilty pleas to similarly reduced charges two weeks ago.

Of the 10 initial defendants, another three -- former Perzel chief of staff Brian Preski, former state Rep. Brett Feese of Lycoming County, and Mr. Feese's former secretary, Jill Seaman -- say they plan to continue to fight their charges at trial later this month.

Elmer "Al" Bowman, an ex-aide to Mr. Feese, has not entered a plea, nor is he listed on pre-trial documents with those defendants.

A final caucus staffer, John Zimmerman, is being prosecuted separately, in a case expected to go to trial in December.

Mr. Perzel is free on bond pending sentencing, which has not been set.