U.S. Rep. Jim Gerlach has agreed to pay what appears to be the largest penalty ever imposed on a Pennsylvania member of Congress for violation of federal campaign-finance laws.

The Chester County Republican will pay $120,000 from campaign funds in installments over the next year to settle a civil case arising mainly from a huge bookkeeping mistake he made after his successful 2004 reelection effort.

Gerlach reported to the Federal Election Commission that he had raised almost $2.2 million in a period of less than two months after the election. In reality, he had raised $18,000 to $20,000.

The mistake was in confusing funds he had taken in earlier with donations he received during the short postelection period. Before it came to his attention, Gerlach said, the error was repeated in FEC reports he filed in April and July of 2005.

In a conference call with reporters yesterday, Gerlach said that the size of the penalty seemed "way out of line" and that he gained nothing from the overstatement. But he said he had decided to pay the fine rather than let the issue drag on, possibly for months, in the FEC judicial process.

Gerlach, who was first elected to the U.S. House in 2002, will be up for reelection next year.

The FEC investigation began with a complaint from Democrat Lois Murphy, who was Gerlach's opponent in two close elections, in 2004 and last year.

Murphy, who appears to have no plans to run again, could not be reached for comment yesterday.

But Carrie James, a spokeswoman for the Democratic Congressional Campaign Committee, said of Gerlach: "The fact that he can't balance his own checkbook doesn't speak to his financial responsibility. . . . I don't know how he can be trusted to restore fiscal responsibility to Washington."

The FEC declined yesterday to comment on the size of the fine, which Gerlach said was determined according to a cut-and-dried formula, taking into account the large amount of the financial overstatement.

The FEC Web site shows that, since 1980, the agency has issued 59 fines of $120,000 or more. Gerlach's penalty is by far the highest for any House or Senate member from Pennsylvania, according to data on the site.

Gerlach admitted to two smaller mistakes that he also described as bookkeeping errors. One was misreporting $8,911 in refunded contributions in 2005. The other was failing to itemize $8,832 in contributions from another fund-raising committee in 2004.

Although Gerlach accepted the ultimate responsibility, he essentially laid the blame for the mistakes on his former campaign treasurer, Alan Randzin.

Randzin, also a Republican, is the elected treasurer of Chester County. He could not be reached for comment yesterday.

"We decided we needed to change treasurers and moved on to somebody else," Gerlach said.

Contact staff writer Tom Infield

at 610-313-8205 or tinfield@phillynews.com.