Congressional Democrats are using the legislative process to pressure Republican presidential candidate Mitt Romney to release more tax returns and information about his investments in offshore accounts.

The push on the Hill represented a full scale legislative assault on Romney over the tax issue, as Democrats sense they may be getting traction over Romney’s refusal to release more than two years of tax information.

In the House, Rep. Sander Levin (D-Mich.) is proposing legislation that would require presidential candidates to release 10 years worth of tax returns and disclose any overseas investments.

And in the Senate, Sen. Dick Durbin (D-Ill.) and Sen. Carl Levin (D-Mich) are proposing beefing up financial disclosure forms for all candidates for federal office to require disclosure of overseas investments, including Swiss bank accounts.

The House bill would also require new disclosure of off-shore investments but specifically targeted the tax return issue. Rep. Sander Levin said Romney should “set the example” for future candidates and release his returns. But then he said the law must be changed so release of tax information is not at the discretion of candidates.

“I don’t think there’s any question now in terms of the responsibility of the candidate,” he said. “I think the law ought to now reflect that responsibility.”

Sen. Carl Levin told reporters that the Senate proposal would shed new light on the use of shell corporations based overseas to help U.S. companies and individuals avoid U.S. taxes. But Durbin confirmed the timing of the proposal is designed to highlight Democratic complaints with Romney’s investments.

“Clearly, I think the American people are entitled to more,” Durbin said, of the two years of tax returns Romney has so far said he will release. “I also think he has an obligation to explain why he and his family decided that offshore tax havens are the right place to park their money and their wealth. Those are legitimate questions.”

The two suggested they would move the item as an amendment to some other larger bill in coming weeks, which could force a Senate floor debate.

Romney has already been dogged by revelations in the returns that he held money on offshore investments in the Cayman Islands and Switzerland. His campaign has said his investments are directed by a blind trust that he does not control. They also say that he has paid all taxes he owed and the offshore investments were not intended to lower his tax bill.

In a Tuesday interview, Romney said he was reluctant to release more records that his political opponents would pick over for information they could use to damage his candidacy.

But Durbin said there is no reason to hold money in a Swiss bank account other than to conceal wealth or to bet on the strength of the Swiss franc over the U.S. dollar.

“I think a member of Congress who takes that position needs to explain that. A candidate who takes that position needs to explain that,” he said, indicating his research shows Romney is the first presidential candidate to have a Swiss bank account.

Pressure has been rising from Republicans as well as Democrats on Romney to disclose more information about his significant personal wealth and his tax bills and the legislative proposals are designed to press the issue again.

As the election approaches, both parties will use their congressional perches to introduce legislation designed to clarify and highlight campaign trail fights.

The Senate proposal would apply to government officials already required to file financial disclosures, including senior legislative aides, senior executives at federal agencies, all candidates for federal offices and incumbent lawmakers. It would require candidates to disclose any financial interest they or their spouses hold in offshore tax havens.

Republicans on the Hill have tried to avoid becoming dragged into the tax return issue. Asked whether Romney has been transparent enough, House Speaker John A. Boehner (R-Ohio) Wednesday said it’s a distraction from the economy.

“The American people are asking, where are the jobs? They’re not asking where in the hell the tax returns are. This is another sideshow intended to draw the American people’s attention away from the real issue,” Boehner said.

Share your thoughts in the comments section below.

Follow Rosalind S. Helderman on Twitter: @postroz

Read more at PostPolitics

The Fix: Obama’s ‘You didn’t build it’ problem

McCain defends Huma Abedin against Muslim Brotherhood accusations

The Fix: The case for Bobby Jindal as Romney’s veep pick