Amplifying the Obama campaign's push for Mitt Romney to release more tax documents, Vice President Joe Biden will make some of his most biting remarks yet in a speech Tuesday attacking the presumptive GOP presidential nominee.

"Mitt Romney wants you to show your papers, but he won't show us his," Biden will say, according to excerpts of prepared remarks released by the president's re-election campaign.

At a Las Vegas speech for the National Council of La Raza convention, a large Latino civil rights group, Biden will carry the torch in the campaign's recent blitz against Romney over reports of his offshore investments.

Team Obama and national Democrats seized on a report last week in the magazine "Vanity Fair," which called Romney a "remarkable financial acrobat," with accounts and investments in several places considered tax havens for Americans - Bermuda, the Cayman Islands and Switzerland.

While the campaign hasn't directly charged Romney with tax evasion, they suggest the millionaire may be hiding important details about his finances by not disclosing multiple years of returns.

In January, Romney released his tax returns for 2010 and an estimate for 2011. Federal campaign law does not require candidates to release tax returns, but it does require candidates to file annual financial disclosure paperwork, which Romney has done.

The re-election team often points to Romney's father, the late George Romney, who released 12 years of tax returns when he ran for president in 1968.

"As he said, 'One year could be a fluke, perhaps done for show'," Biden will say, referring to George Romney's stated reason for putting out a dozen years of documents.

Biden will continue: "His son has released one year of his tax returns. Making a lie of the old adage: Like father, like son."

Romney responded Monday to the recent barrage of attacks, saying his foreign investments have been held in a blind trust and managed by a trustee. The candidate emphasized he has no knowledge of where his money is being placed.

"I don't manage them. I don't even know where they are," Romney said in an interview with Radio Iowa.

Romney further reiterated he was in no violation of tax law.

"That trustee follows all U.S. laws. All the taxes are paid, as appropriate. All of them have been reported to the government. There's nothing hidden there," the candidate said, arguing the president was trying to "divert attention" from his own record.

A surrogate for Romney, Rep. Jason Chaffetz of Utah, came to the candidate's defense on Tuesday, saying it was time for Democrats to let go of the issue.

"He's released everything that he's required to release including paying more than sixteen percent of his income to charitable giving," the Republican congressman said on CNN's "Starting Point." "Governor Romney's been very successful. Get over it."

-- CNN's Paul Steinhauser and Gregory Wallace contributed to this report.