Updated: 7:56 p.m.

Rep. Todd Akin apparently has personal assets far beyond what he has previously revealed on his annual financial disclosure forms.

Last week, the Missouri Republican amended nearly a decade’s worth of personal financial disclosure forms, reporting assets for 2010 worth a minimum of $355,000, more than 10 times what he had reported in May.

Akin, who is challenging Sen. Claire McCaskill (D-Mo.) in 2012, told House ethics officials in a letter last week that he has partial ownership of two pieces of property in an affluent St. Louis suburb and a third in East Dennis, Mass.

His stake in the three properties was worth more than $324,000 in calendar year 2010, according to the letter, dated July 19. On the original disclosure form that he filed in May, Akin had reported only a series of stocks and retirement accounts, with a minimum value of about $31,000.

A spokesman for Akin said the six-term Congressman originally thought he was not required to disclose the assets because they generated no income and because he had no legal control over them. But in May, questions from the St. Louis Post-Dispatch prompted him to seek the guidance of the House Ethics Committee, which in a letter dated July 12 advised him to report the real estate.

Akin, his three siblings and his father share partial ownership of a pre-war home where they were raised on two abutting properties in Town and Country, Mo., a wealthy neighborhood about 10 miles west of downtown St. Louis.

The amendment states that Akin’s portion — including that of his wife and dependent children — of the 10-acre property, held in a limited partnership, is worth almost $65,000. He listed values for the property for every year since Akin took office in 2001, including some years in which the value exceeded $124,000. The city of St. Louis has appraised the two lots at about $750,000.

Steve Taylor, Akin’s spokesman, said the property has never been rented or generated any income.

But that could change very soon. The family is poised to demolish the Missouri home and divide the land into eight plots for individual development that could deliver significant financial gain, Taylor said.

Akin lived in the home until he moved to Wildwood, Mo., earlier this year, he said.

Akin’s portion of the Cape Cod real estate, held in a limited liability corporation established in 2009, is worth almost $260,000. The home has an assessed value of $3.2 million according to local property records.

Akin’s new filings arrived at the start of a campaign that has already been churning with ethics allegations.

The Missouri Republican Party filed a complaint with the Federal Election Commission on Monday accusing McCaskill of violating campaign finance laws by failing to report more than $500,000 in contributions and disbursements from her 2006 campaign. McCaskill last week filed hundreds of pages of amendments to her prior FEC filings to account for the discrepancies, which she said were routine bookkeeping errors.

“Senator McCaskill’s reporting violations are massive and ongoing — and they have taken five years to come to light,” Lloyd Smith, executive director of the Missouri Republican Party wrote in the complaint.

Missouri Republicans have been hammering McCaskill on ethics issues since it was revealed this spring that she had failed to pay property taxes on an airplane that she owns and had paid for some flights with taxpayer money.

“Clearly the Missouri Republican Party is making desperate accusations about Claire in a sad attempt to diffuse a decade’s worth of possible ethical violations that Congressman Todd Akin was forced to amend on reports after being caught by a his hometown newspaper,” said Caitlin Legacki, a spokeswoman for the Missouri Democratic Party.

Akin faces former Missouri Treasurer Sarah Steelman in the Republican primary to take on vulnerable McCaskill.