PHILADELPHIA (CBS) –  Frank Rizzo Jr., who is in his final few months on Philadelphia City Council (see related story), has decided to leave the Republican party — a change prompted by a spat with a fellow Republican on Council.

City Council’s GOP leader, Brian O’Neill of the 10th District, had been unhappy that Rizzo voted against him in a recent battle over redistricting.

So, O’Neill last week stripped Rizzo of his post as minority whip, a mostly ceremonial position given that Council has only three GOP members.

Rizzo blasted the move:

“An immature act, an act of abuse of his power, to do something like that based on a vote,” he told KYW Newsradio.

(Frank Rizzo's new voter registration.)

And now, Rizzo has now fired back:

“I’ve changed my registration.  I’m no longer a Republican.”

Rizzo is now registered as unaffiliated.

This was O’Neill’s reaction:

“He’s going out of office.  He’s obviously very bitter over his loss in the primary, and he’s taking it out on anybody he can.”

Rizzo has served three terms on Council, as a Republican.  His father served two terms as mayor of Philadelphia, running both times as a Democrat, but changed his party affiliation to Republican in 1986 to run for a third term.

Reported by KYW City Hall bureau chief Mike Dunn