Companies including Duke Energy Corp, Bank of America Corp and AT&T Inc spent millions of dollars to help stage last month's Democratic convention, technically complying with the party's restrictions on corporate funding, financial disclosures revealed on Wednesday.

The convention, where President Barack Obama officially accepted his nomination on Sept. 6, marked the first time the Democratic Party, seeking to set an example, had set limits on sources of funding. It banned donations from corporations and lobbyists and capped individual donations at $100,000.

But several large corporations contributed free-of-charge goods and services to the account funding the Democratic National Convention. Scores more donated to a separate fund exempt from those limits because it was meant to finance activities "of ongoing value" to the host city of Charlotte, North Carolina, and not the Democratic event itself.

Republicans had no similar restrictions on donations for their convention.

Labor unions, a traditional source of cash for the Democrats, gave $3 million.

Charlotte-based Duke Energy was the strongest corporate financial muscle behind the Democratic convention, giving $1.6 million in in-kind donations by providing office space and furniture, travel, consulting and parking spaces, according to Federal Election Commission disclosures

The company wrote another $4.1 million check to the second, separate fund, called New American City. Chairman Jim Rogers contributed a total of $339,523 in both regular and in-kind donations for travel and personal staff expenses for fundraising, according to the filings.

Duke also guaranteed a loan that convention organizers had to take out to cover a money shortfall, Democratic officials said.

AT&T financed $298,562 worth of "delegate bags" and "catering for suites" for the main convention fund and gave $1 million to the New American City fund, filings showed.

Bank of America, also based in Charlotte, contributed $271,864 worth of furniture and office space to the convention and gave $5 million to the New American City fund.

Microsoft Corp contributed $71,521 worth of catering, the Coca-Cola Company funded $69,590 worth of delegate bags and Costco bought $27,000 worth of food and service items. Half Moon Bay Brewing Co provided $5,000 worth of beer and Chiquita Brands International Inc supplied $4,000 worth of bananas, among others.

"Beyond showcasing Charlotte for the entire world, the convention generated millions of dollars in economic activity for our community and valuable infrastructure improvements," said Dan Murrey, executive director of the host committee.

"We have accomplished all of this without passing any of these costs on to the taxpayers."

In all, the main "Charlotte 2012" fund sponsoring the convention raised $24.1 million. But it came up short of the necessary funds and had to take out a $10.9 million loan. Organizers still owe almost that amount after spending $29.9 million.

The New American City, for its part, raised $19 million and spent $19.6 million. It also holds $1.3 million in debt.

The fund's other biggest donors included Time Warner Cable Inc, meetings and events planning firm Experient Inc, Wells Fargo & Co bank and Charlotte-based Mechanics & Farmers Bank.

The biggest labor union donors, giving $500,000 each, were the Service Employees International Union, the American Federation of State, County and Municipal Employees and the United Association of Journeymen and Apprentices of the Plumbing and Pipe Fitting Industry.