After two earlier false starts, the House approved a $1.7 billion fiscal 1986 supplemental appropriations bill yesterday that attempts to strip President Reagan of power to defer authorized spending.

The White House, objecting to the deferral provision and other sections of the bill, has threatened to veto the measure, which passed the House 242 to 132.

The bill, which now goes to the Republican-controlled Senate, would also overturn more than $5.3 billion in spending deferrals that Reagan has made for this fiscal year.

House Republicans made two ill-fated attempts block the proposed elimination of the president's deferral authority. Describing the deferral process as in "chaos," Rep. Leon E. Panetta (D-Calif.) said, "We are no longer able as an institution to challenge deferrals."

He said some spending deferrals "make sense" as a management tool, but added, "We have to send a clear message to the administration that we're fed up with this process."

Legislators have been complaining about the process since a 1983 Supreme Court decision barred "one house" vetos, the power of a single chamber to overturn presidential decisions -- such as deferrals. Some lawmakers charge that the process now gives the president too much power.

The Reagan deferrals that would be overturned by the measure include $2.7 billion for low-income housing, almost $600 million for housing for the elderly and handicapped and $500 million for community development block grants. Other major items in the bill include:

*$702 million to beef up security at U.S. diplomatic posts around the world, the first part of a $4.4 billion security-enhancement program. The administration seeks new funds for this purpose, but the House bill instead transferred the $702 million from Defense Department and other government accounts.

*$272 million for Veterans Administration compensation and pension programs, and $91 million for readjustment benefits.

*The first $50 million in a planned $250 million economic aid package for Northern Ireland. Rep. Robert S. Walker (R-Pa.) sought to cut this to $20 million, the administration's request for this year, but lost 241 to 157.

*New appropriations of $250 million for federal disaster relief, $340 million for the Internal Revenue Service, $80 million for the Federal Aviation Administration and $20 million for the Women, Infants and Children nutrition program.

Several of the new appropriations in the bill would effectively offset the across-the-board spending cuts that were imposed this year under the new Gramm-Rudman-Hollings balanced-budget law. The specific spending limits and targets are not mandated under that law until the fiscal 1987 budget.

The bill was withdrawn in April after it became entangled in legislation to provide military aid to the Nicaraguan rebels -- known as contras or counterrevolutionaries -- and later that month because of a revolt of Agriculture Committee members who objected to some proposed farm policy changes. The most controversial farm provisions were removed from the bill yesterday.