The House voted yesterday to bar the Reagan administration from imposing any policy that would reduce the number of takeoffs and landings at National Airport below the level reached on the Friday before the air controllers' strike began.

The vote threw into question the administration's carefully crafted noise and congestion policy for the airport. As now constructed, the policy, which is scheduled to become effective in October, would reduce flight operations slightly from prestrike levels, according to the Federal Aviation Administration.

The House's action came on a 204-to-188 vote to amend a transportation appropriations bill that subsequently was passed. It now goes to the Senate, which has yet to consider the measure.

Area political and civic leaders immediately condemned the House move as interference in their decade-long attempt to control noise and congestion at the airport. They argued that airport policy is a local concern and that Congress is more concerned about its own convenience.

Transportation Secretary Drew Lewis, who unveiled the plan in July, assailed the House move and pledged to continue to work for its implementation. One of the plan's major supporters on the House floor, Rep. Frank Wolf (R-Va.), suggested the Senate might reverse the vote. "I'm not giving up; I don't think we've lost the battle," he said yesterday.

Eric Bernthal, president of the civic umbrella organization Coalition on Airport Problems, said the House's intent was to undo the entire policy. "If there's a legal basis to challenge this in court, you better believe we will," he said.

Whatever the debate's outcome, the airport plan will have little immediate effect on traffic levels at National because the air controllers' strike has already reduced traffic there by about 25 percent, far more than even the administration's version could do.

With most of its controllers fired, FAA officials predict it will take several years to rebuild the air control system to handle prestrike traffic levels. Area civic and political leaders, having worked for a decade to regulate aircraft noise along the Potomac, want to assure the right policy is in effect as traffic expands.

The House amendment to the policy was introduced by Rep. Charles Wilson (D-Tex.), primarily because he wanted to preserve competition at National where relatively new low-fare lines like New York Air are challenging the established airlines, according to his press secretary, Julie Anne Booty.

"He's afraid that if they reduce the number of flights, it won't be Eastern that will suffer," Booty said, "but some of the low-fare lines will be squeezed out."

Wilson became interested in the issue, she said, when someone from Texas International, the parent company of New York Air, spoke to him about it.

The plan also would impose immediate noise restrictions and then tighten them in 1986, cap National's passenger load at 16 million per year and improve access to Dulles International, in an attempt to attract airlines and passengers to the underused terminal there.

The FAA, members of Congress and civic activists give conflicting appraisals as to whether these rules would reduce traffic, if at all. This is because many potential loopholes remain in the plan.

However, the FAA and most other analysts agree that the plan probably would mean at least some reduction over prestrike operations, with estimates running as high as 10 percent.

On a typical Friday before the strike, there were between 725 and 755 takeoffs and landings by commercial airliners and air taxis, according to Harry Hubbard, chief of National's control tower. On that basis, the House amendment would appear to require more access to the airport than the administration wants.

Public comment on the policy closed Aug. 31 and the FAA now is giving the policy a final review, with implementation planned for Oct. 26. Congress has no formal powers to review it. But, by attaching riders to the appropriations bill that would fund its implementation, legislators can enforce their feelings.