WASHINGTON – For nearly 15 years, Republican presidential candidate Mitt Romney's financial portfolio has included an offshore company that remained invisible to voters as his political star rose.

Based in Bermuda, Sankaty High Yield Asset Investors Ltd. was not listed on any of Romney's state or federal financial reports. The company is among several Romney holdings that have not been fully disclosed, including one that recently posted a $1.9 million earning — suggesting he could be wealthier than the nearly $250 million estimated by his campaign.

The omissions were permitted by state and federal authorities overseeing Romney's ethics filings, and he has never been cited for failing to disclose information about his money. But Romney's limited disclosures deprive the public of an accurate depiction of his wealth and a clear understanding of how his assets are handled and taxed, according to experts in private equity, tax and campaign finance law.