Massachusetts Rep. Barney Frank announced Monday that he would retire at the end of his term in early 2013, citing his redrawn district boundaries and his desire to write as reasons.

A longtime liberal stalwart on Capitol Hill, Frank said that he would leave the House after 16 terms primarily due to the way his 4th congressional district had been remapped as a result of Census-based reapportionment.

"I was planning to run again, and then the congressional redistricting came," he said at a press conference in Massachusetts.

Frank said that he wasn't particularly interested in the rigors of waging a full-fledged campaign -- particularly fundraising -- in a district that was mostly half new to him.

As chairman of the House Financial Services Committee, Frank coauthored of 2010's financial regulatory reform law; he serves now as the committee's ranking Democratic member. Frank said he had been flirting with retirement for some time now, but was motivated to return to Congress for another term to help defend the law from Republicans who have pledged to repeal the law.

Frank also denied that Democrats' chances of winning back the House next fall played a major role in his decision to decline re-election.

Frank has long been a lightning rod for critics, in no small part because of his blunt comments to the press, and sometimes cantankerous engagements with Republicans. But for conservatives hoping that Frank fades into a quiet retirement, the outgoing congressman promised anything but that.

"I'm not retiring from advocacy of public policy," he said. Frank said his preference would be to write -- perhaps on an unfinished Ph.D. dissertation -- and speak freely on issues. He said he didn't anticipate practicing law, though he suggested he "might show up pro bono someday for a gay rights case." (Frank is one of only three openly gay members of Congress.)

Frank also swore off becoming a lobbyist (He would be in a prime position to cash in because of his committee position.), while taking a shot at former House Speaker Newt Gingrich at that.

"I will neither be a lobbyist nor a historian," he said, referencing Gingrich's explanation at a recent debate of his work for troubled mortgage giant Freddie Mac as being in his capacity as a historian. "One of the advantages to me of not running for office is I don't even have to try to pretend to be nice to people I don't like ... and the notion of being a lobbyist, and having to go and try to be nice to people I don't like -- it would be ridiculous."

Gingrich and Frank have sparred publicly over the course of their respective careers, most recently when Gingrich suggested that Frank should be jailed for the policies the Massachusetts Democrat had supported, which Gingrich said had effectively triggered the housing crisis.

"I did not think I've lived a good enough life to be rewarded by Newt Gingrich being the Republican nominee. It still is unlikely, but I have hopes. I think he is," he said, calling the former Speaker's boomlet a repudiation of former Massachusetts Gov. Mitt Romney.