"We do American business - and the American people - no favors when we turn a blind eye to excessive leverage and dangerous risks," Obama said.
The presidential candidate spoke not far from Wall Street, hard hit by the mortgage meltdown and credit problems.
To fix the economy, Obama proposed relief for homeowners and an additional $30 billion stimulus package to address the nation's economic woes.
"If we can extend a hand to banks on Wall Street, we can extend a hand to Americans who are struggling," he said.
New York Mayor Michael Bloomberg, the almost candidate, introduced Obama but stopped short of an endorsement.
Bemoaning the United States' economic woes, Obama dismissed Republican rival's approach as pure hands-off. On Tuesday, McCain derided government intervention to save and reward banks or small borrowers who behave irresponsibly though he offered few immediate alternatives for fixing the country's growing housing crisis. Obama said McCain's plan "amounts to little more than watching this crisis happen."
Instead, Obama said, the next president should:
While he laid out a half-dozen principles for closer scrutiny of the financial markets, he offered no specifics, such as which agencies should be reorganized or exactly how the government should go about peering over the shoulders of bank executives.
Obama's Democratic rivalplanned a speech on the economy Thursday in Raleigh, North Carolina.
Even before Obama finished his speech, McCain said in a statement, "there is a tendency for liberals to seek big government programs that sock it to American taxpayers while failing to solve the very real problems we face."
The political debate comes as a new government report shows the economy nearly sputtered out at the end of the year and is probably faring even worse amid continuing housing, credit and financial crises.
The U.S. Commerce Department reported that gross domestic product - the value of all goods and services produced in the country - increased at a feeble 0.6 percent annual rate in the October-to-December quarter. The reading - unchanged from a previous estimate a month ago - provided stark evidence of just how much the economy has weakened. In the prior quarter, the economy clocked in at a sizzling 4.9 percent growth rate.