The House, in a stinging rebuke of Speaker Jim Wright (D-Tex.), yesterday defeated a Democratic plan to provide $30.8 million in new humanitarian aid to the Nicaraguan contras.

The leadership plan was defeated 216 to 208, as 45 Democrats joined all but five Republicans in voting against it. The 45 Democrats included about 20 conservatives, who like the Republicans found the Democratic plan so flawed that they preferred to leave the Nicaraguan rebels at least temporarily without U.S. assistance.

But what ultimately sunk it was the 14 Democrats who abandoned the leadership's plan on final passage. The 14 were mostly liberals who opposed any aid to the rebels but had helped the leadership narrowly win a key preliminary vote -- as did 171 Republicans.

Wright, asked why he failed to keep a better hold on his Democratic colleagues, quoted Will Rogers: "I don't belong to any organized political party. I'm a Democrat."

Some Democrats angrily blamed Republicans, charging they sacrificed a cherished cause for temporary partisan advantage, and vowed to do little to help resurrect a contra aid package in the future.

Republicans, however, said that the Democratic proposal to provide only food, clothing, shelter and medical help would have been worth little to the rebels fighting the Marxist Sandinista government. They predicted the Senate could revive the issue by attaching a more militant version to other legislation, or President Reagan could do so on a supplemental appropriations bill.

"It's what we hoped for," said Rep. Mickey Edwards (R-Okla.), the Republican floor leader on the contra aid package. "We're not abandoning the contras, but what we had was nothing. It was just a lousy, lousy bill."

Reagan, in Brussels attending a NATO summit, said he was pleased the proposal was defeated. In a written statement released here, he urged the House and Senate to develop a new, effective aid package "to sustain the Nicaraguan freedom fighters." If they do not, "prospects for peace and democracy inside Nicaragua will diminish quickly," he said.

Edwards suggested that Wright now has an obligation to tailor a new package more along the lines of a Republican alternative that the GOP was blocked from offering yesterday by a Democratic procedural maneuver. Unlike the Democrats' proposal, the alternative would have continued some "nonlethal" assistance such as jeeps and spare parts, would have permitted the CIA to continue making deliveries, and would have guaranteed Reagan another vote later this year on a true military aid package.

Republicans rejected charges such as one from Rep. Dan Mica (D-Fla.), who said: "Rather than get anything, they walked away."

"The Republicans decided the contras weren't worth it," charged Rep. Tony Coelho (D-Calif.), the majority whip. "We will not let it come up {again} except in the regular process," such as during consideration of appropriations bills later this year, he said.

A contra spokeswoman said the vote won't destroy the rebel movement but will put it on the defensive in talks with the Sandinista goverment. The Sandinistas "will become even more intransigent and more hard-line," said Marta Sacasa in Miami. She said the contras are fighting an enemy that continues to receive aid from the Soviet Union.

The Sandinista government reacted cautiously, calling the vote "an opportunity for the Reagan administration to end all aid to the mercenary forces," a term the government routinely uses to describe the contras.

The stunning reversal for the Democratic leadership came on the second of two key votes yesterday. The Democrats won the first, a 215-to-210 vote to adopt their bill as a substitute to a Republican alternative.

But immediately afterward, when it came time to pass the Democratic package, 14 Democrats, most of them liberal, switched allegiance and voted against their party. In addition, the Democratic leadership, which had captured only three Republicans on the first vote, picked up only two additional on the second, far fewer than they had anticipated.

The plan also attracted fewer moderate and conservative Democrats than the leadership expected on a vote to continue at least some level of aid to the contras. "We assumed there would be enough moderate-to-conservative {Democrats} who would say this was better than nothing," said Rep. Barney Frank (D-Mass.), a liberal who supported the leadership on both votes.

Yesterday's vote came exactly a month after the Democratic leadership engineered the defeat of a White House request for $36.2 million for the rebels. That request was a mixture of weapons, military support assistance and humanitarian aid. To ensure last month's victory, Wright promised a key group of moderate Democrats that he would bring a purely humanitarian aid package to the floor of the House.

Wright, who said supporters of military aid to the rebels had won a "somewhat pyrrhic victory" yesterday, showed little inclination to retool the Democrats' aid package to try to attract more support.

But Senate Select Committee on Intelligence Chairman David L. Boren (D-Okla.) said that if the House does not move to resurrect the aid bill, he will try to draft a bipartisan plan to renew shipments of nonlethal aid.

He said it would include provisions for inspection of cargoes to guarantee against shipment of weapons or other lethal material and provide special procedures for consideration of future presidential request for military assistance.

Boren said he thinks there are bipartisan majorities in both houses for such a plan and said the nation has a "moral" commitment to continue humanitarian aid. He said they cannot last for more than 30 days without aid.

Sen. Larry Pressler (R-S.D.), a member of the Foreign Relations Committee and contra-aid supporter, said he thinks it would be "tough" to resurrect the legislation in the Senate, but added that he thinks "the Democrats will find some way to protect themselves" in both houses.

Asked if it would be possible to construct a bill that a majority of the House could support, Wright said, "I don't have that sense as a result of that effort."

The Democratic aid package was developed during several weeks of difficult intraparty negotiations. It was designed to convince liberal Democrats -- many of whom have never voted for aiding the contras in any fashion -- that continuing humanitarian assistance would be the best defense against future attempts by the Reagan administration to resume lethal aid.

In developing the proposal, Democratic leaders kept their commitment to a small group of moderate Democrats whose votes were critical to the Feb. 3 defeat of a $32.6 million administration proposal, which included $3.6 million in direct military assistance as well as additional funds for logistical support such as helicopter spare parts. The humanitarian aid proposal was designed to allow those moderates and other lawmakers to argue that Congress has continued to press both sides in the Nicaraguan civil war to seek a lasting peace.

The Democratic plan would have provided a total of $30.8 million in assistance over four months, and would have prohibited any resumption of military aid, which was terminated at the end of February.

Of the total, $14.56 million would have gone to buy the rebels food, medicine, clothing and shelter, and the means of transporting it. A like amount was to be used to provide medical treatment to young victims on both sides of the prolonged conflict. The remainder, $1.44 million, would have gone to Nicaraguan Indian groups who have fought the Sandinista regime.

The defeated plan also would have ended the CIA's role in overseeing the assistance and transferred supervisory authority to the Defense Department -- subject to strict inspections by congressional intelligence committees and the General Accounting Office.

The legislation also would have set up a procedure under which Congress could vote on a further aid request in June, but only if the House Permanent Select Committee on Intelligence -- controlled by Democrats -- certified that a cease-fire was not in place and that the breakdown of the peace process was the fault of the Sandinista government.

The $36.3 million Republican alternative, which GOP leaders were prevented from offering, differed in several key respects. Although it also included no direct military aid, it would have allowed shipments of nonlethal assistance, including jeeps and spare parts. It also would have continued CIA deliveries, and guaranteed Reagan another congressional vote within 45 days on a new military aid package.

In the Maryland delegation, Democrat Beverly B. Byron and Republican Helen Delich Bentley voted against the Democratic plan, while Democrats Benjamin L. Cardin, Roy P. Dyson, Steny H. Hoyer, C. Thomas McMillen and Kweisi Mfume and Republican Constance A. Morella voted for it.

In the Virginia delegation, Republicans Herbert H. Bateman, Thomas J. Bliley Jr., Stan Parris, D. French Slaughter Jr. and Frank R. Wolf voted against the package, along with Democrat Rick Boucher. Democrats Jim Olin, Owen B. Pickett and Norman Sisisky voted for the plan.

Staff writers Helen Dewar and Don Phillips in Washington and correspondent Julia Preston in Managua contributed to this report.