Ignored by controlling Democrats in Lt. Col. Oliver North's testimony was his explicit, repeated charge that ''secret Israeli agent'' Manucher Ghorbanifar -- with a push from government officials in Israel -- originated the scheme to divert profits from Iranian arms sales to the Nicaraguan contras.

That Iran-contra committee Democrats would turn their heads from this explosive testimony suggests the bond between the pro-Israel lobby and such powerful figures in the party as Sen. Daniel Inouye, the Senate chairman. This link may also explain the committee's tilt, predicted at the White House and reported by us in December, to concentrate on the contras and ignore Iran.

Part of the committee's protective cloak over Israel is its reluctance to summon Michael Ledeen, who as a part-time National Security Council consultant appears to be the first American to discuss selling arms to Iran with Israel. Then-national security adviser Robert McFarlane has told us that when Ledeen informed him about an early 1985 trip to Israel, he replied: Okay, Mike, but you are on your own hook. That trip triggered the Iran ''initiative'' that has brought obloquy to Ronald Reagan.

Although Ledeen visited then-prime minister Shimon Peres' office to discuss the ''initiative,'' Inouye appears to feel the public interest would not be served by putting him on the stand to learn what the Israelis said. Ledeen twice has given secret depositions, but committee staffers told us the ''on-again, off-again'' plan to bring him before the committee is now ''off.''

That typifies the congressional investigation's intensity in pursuing North's tantalizing testimony about Ghorbanifar. Invariably called ''an Iranian middleman'' by the news media, Ghorbanifar was described by North quite differently: a ''secret Israeli agent,'' words North directly attributed to the late CIA director, William J. Casey.

Republican Sen. James McClure, an administration supporter, was the only committee member at this writing to risk political problems with the pro-Israel lobby by asking direct questions about Ghorbanifar's role. A gripping exchange between the senator and North was ignored by McClure's colleagues on the committees and the national media in general.

''I believed then and I believe now,'' North told McClure, that Ghorbanifar was an Israeli agent whose apparent task was to find some way to sell North -- and through him the Reagan administration -- on continuing the dying Iran-arms scheme. How? By the inducement of diverting profits to the contras.

''And that was the genesis of the connection between Iran and the contras?'' asked McClure. Yes, replied North, who went on to reveal that Israel pushed hard to send Iran antitank TOW missiles, though anti-aircraft Hawk missiles were requested by Tehran. Was it Israel's rationale, McClure asked, to give Iran enough TOWs to destroy Iraq's tank force and thus handle the ''concerns the Israelis had with Iraqi armor''? Yes, North replied.

McClure noted that Al Schwimmer, usually described as a private Israeli arms dealer and a key player in the early dealings with Ledeen, holds both U.S. and Israeli citizenship and has served in this country ''as a registered foreign agent for the Israeli government.'' The senator did not say so, but the implication was: Why not subpoena Schwimmer, who may not have diplomatic immunity?

All this passed with little show of interest by the committee or Inouye, an important and respected Democratic figure nationally and in the Senate. He received $48,825 during the 1985-86 election cycle from fund-raising PACs found in a Wall Street Journal survey last month to be linked to the American Israel Public Affairs Committee. His reelection in Hawaii last November was never in doubt, and he won with 74 percent.

Inouye voted against Reagan's appeal to sell AWACS aircraft to Saudi Arabia in 1982 and voted to override Reagan's veto of the congressional ban on another arms sale to Saudi Arabia in 1986. He signed a letter to Reagan demanding withdrawal of the president's plan to sell Stinger missiles to Jordan in 1984 and originated a losing effort to give Israel special concessions against budget damage from Gramm-Rudman spending limits. That record is not unusual with members of Congress who feel committed to supporting Israel, however unselfish their reasons.

But as chairman of the most important congressional investigation since Watergate, Inouye has failed to stock the Israeli file with all the facts and threatens to leave a distressingly incomplete record. The tough World War II hero who has intrepidly insisted on uncovering every embarrassing detail of the contra support operation so far has flinched when Israel was mentioned.