Witnesses are being lined up for yet another congressional hearing over the Oil-for-Food (search) scandal, which has rocked the United Nations (search) and pushed lawmakers to demand the international organization make more efforts to cooperate — or else.

"My friend, [Rep.] Henry Hyde and I are determined to get to the bottom of this and any other scandals that may be around the U.N.," Rep. Tom Lantos (search) of California told FOX News on Thursday. "But the U.N. reflects the world as it is in all its ugliness."

Lantos is the ranking Democrat on the House International Relations Committee (search), one of five congressional panels probing allegations of fraud, abuse and mismanagement of the $60 billion Oil-for-Food program.

The Senate Permanent Subcommittee on Investigations on Thursday announced that is has scheduled a hearing entitled, "The United Nations' Management and Oversight of the Oil-for-Food Program," for Tuesday at 9:30 a.m. EST. This is the second of several hearings the subcommittee intends to hold on the misappropriation of cash from the humanitarian relief program.

The House International Relations Committee's newly-formed Subcommittee on Oversight and Investigations held a hearing Wednesday to examine the interim report on the scandal released by Paul Volcker's (search) Independent Inquiry Committee. Volcker and his panel were commissioned by U.N. Secretary General Kofi Annan (search) to investigate the program.

Lantos said he recently talked to Annan, "and I told the secretary-general that they have to clean up their act, and I believe Kofi Annan has the personal integrity and the capability to do that."

Annan has specifically come under fire for his role in the program, since he is head of the international organization that was overseeing the program. British Prime Minister Tony Blair (search) on Thursday voiced unconditional support for Annan, who is now pushing for various U.N. reforms.

The U.N. chief is also being eyed after news surfaced that his son, Kojo Annan (search), previously worked for Cotecna (search), a company that won a contract to handle humanitarian relief entering Iraq. Some — such as Sen. Norm Coleman, the Republican senator from Minnesota who sits on the Senate Permanent Subcommittee on Investigations — have gone so far as to call for Annan's resignation.

Other lawmakers aren't going to that extreme but many agree that massive reform is needed.

"I have no doubt in my mind that if the facts indicate it, he will do so," Lantos said of whether Annan would be willing to investigate his own son if that's what it takes to get to the bottom of the scandal. "I don't believe you're responsible for your adult children … they make their own decisions."

Nevada Sen. John Ensign, who has introduced legislation that would penalize the United Nations unless it puts forth the information requested by Congress, told FOX News on Thursday that it's imperative to hold someone at the United Nations responsible to avoid future problems like those that plagued the Oil-for-Food program.

"We want to make sure not only that we get the information, but we want, if there were actually problems with it, that we want the whole United Nations accountable. The U.S. should not continue to foot the bill for the United Nations without some sort of accountability," said the Republican lawmaker.

"I think that the United Nations has become largely ineffective in its role in the world and it's things like the Oil-for-Food scandal that have shown that," Ensign continued. "It's inefficient, ineffective and now, perhaps corrupt."

Ensign is one of the lawmakers claming that the United Nations has been anything but forthcoming in making sure congressional lawmakers have all the information they've requested regarding the program.

"The United Nations, they want to do their own internal investigation. Paul Volcker has said he would make everything public when he was finished but he didn't want anything to interfere with his investigations. We disagreed with that," Ensign said. "The United Nations is cloaked in secrecy. They're not accountable to anybody in the world and we need to get to the bottom of it if the United Nations is to have any accountability whatsoever."

Rep. Joe Barton, R-Texas, this week wrote to Annan's new chief of staff, Mark Malloch Brown (search), who was on Capitol Hill on Wednesday to meet with lawmakers and discuss U.N. reforms. Barton disputed recent comments Brown made indicating that the United Nations is cooperating with congressional investigators.

"The Volcker report makes it clear that abuse of the Oil-for-Food program was rife, and the U.N.'s reluctance to be forthcoming is troubling," added Rep. Jeff Flake, the Arizona lawmaker who serves as vice chairman of the House International Relations Subcommittee on Oversight and Investigations.

"The U.N. has had more than enough time to prove their willingness to cooperate, yet they have chosen not to. I believe it’s time for Congress to take action and force the U.N. to cooperate," Flake said.

Flake introduced legislation last year that would condition a portion of U.S. funding to the United Nations on the international body's cooperation in the investigation. Flake is expected to reintroduce that bill "shortly," according to his office.

Hyde, the Illinois Republican who serves as chairman of the House International Relations Committee, wrote a letter to Annan on Wednesday requesting audits on the World Meteorological Organization (search) and 15 other U.N. agencies, thereby expanding his committee's probe of abuse to U.N. organizations other than those responsible for Oil-for-Food.

FOX News obtained a series of cables to the State Department from the U.S. mission to the United Nations in Geneva, outlining an apparent multimillion-dollar scandal at the World Meteorological Organization, a Geneva-based U.N. agency. A Sudanese U.N. employee allegedly skimmed $3 million over a three-year period and up to 15 officials at the agency have been implicated as being guilty of negligence.

What is even more disturbing to congressional advisers, however, is a statement from the auditors that "WMO's internal procedures were not the worst seen in the U.N. family of organizations."