Robert Gibbs, a top campaign adviser to President Barack Obama, called on Romney to release more than the two years' worth of tax returns he has so far made public as a way to answer questions about his investments.
"This is a guy whose slogan is 'Believe in America,' and it should be 'business in Bermuda,'" Gibbs told CNN's "State of the Union".
Democratic Party chairwoman Debbie Wasserman Schultz told "Fox News Sunday", "Americans need to ask themselves, why does an American businessman need a Swiss bank account and secretive investments like that?"
"I've never known of a Swiss bank account to build an American bridge, a Swiss bank account to create American jobs, or a Swiss bank accounts to rebuild the levies to protect the people of New Orleans," Maryland Governor Martin O'Malley told 'This Week'.
The seemingly coordinated attacks immediately preceded the release of ads by Obama camp's "Truth Team" and DNC capitalising on renewed focus on Romney's offshore finances after a Vanity Fair report released last week.
The report reveals a corporation set up in 1990 in Bermuda owned by Mitt Romney and revisits details of his Swiss Bank account and offshore tax havens.
Much of Romney's fortune lies well hidden in a network of opaque offshore investments including some USD 30 million in the Cayman Islands, Vanity Fair had reported, adding he also holds a Swiss bank account -- with USD 3 million in it, according to 2010 tax returns -- and other interests in tax havens such as Bermuda. (More)