Sen. Bob Menendez, D-N.J., whom a federal grand jury had indicted on corruption charges in April, accused prosecutors of violating the independence of Congress.

On Monday, the lawmaker from New Jersey asked a federal judge to throw out the charges against him in what the New York Times called an "aggressive response" to the Justice Department's accusations that he traded political favors for luxury vacations, free airfare and campaign donations.

The Democrat's case is seen as a likely precedent on how far federal investigators can go when they look into potential corruption on Capitol Hill, and its outcome could have important ramifications for years to come, the newspaper commented.

The senator's lawyers said that prosecutors failed to call before the grand jury witnesses who could have backed Menendez, NJ.com reported. Menendez's attorneys noted that top-ranking officials with Medicare would have testified that the senator had never asked them to intervene in a reimbursement dispute involving his longtime friend, Salomon Melgen, a Florida eye doctor who is also facing charges.

"In an effort to make those meetings appear to the grand jury to be about Dr. Melgen, the prosecutors did not call the people who were present at the meetings to testify before the grand jury," the attorneys wrote. "Instead, they asked a case agent, eager to say 'yes' to confirm that the prosecutors were right."

Menendez is the first member of the Senate to face federal bribery charges since the 1980s, when Harrison Williams, also a Democrat from New Jersey, was indicted as part of the federal corruption investigation known as Abscam, the New York Times recalled. Alaska Republican Ted Stevens' 2008 conviction for lying about gifts on Senate ethics forms, meanwhile, was later thrown out due to alleged prosecutorial misconduct.

A key argument made by the legal team is that Menendez's actions were part of his congressional oversight responsibilities, which are protected by the Constitution's "speech or debate" clause that prohibits the Justice Department from interfering with the legislative process.

"The prosecution has no direct evidence ... that there ever was a quid pro quo agreement between Senator Menendez and Dr. Melgen (because no such agreement ever occurred)," the lawyers wrote.