The House yesterday overwhelmingly approved President Carter's plan to give free food stamps to needy people, and knocked down bids to ban the stamps for strikers or forbid their use for junk foods.

The votes came as a farmer-consumer coalition of House members moved toward completion of section of the pending omnibus farm-food bill overhauling the $5.6 billion food stamp program and extending it for four years.

By a 317-to-102 vote, the House rejected an effort by Rep. Stephen D. Symms (R-Idaho) to strike Carter's plan from the stamp bill and restore an existing regulation under which needy people buy part of their monthly stamp allotments.

Under existing regulations, a family of four with a net income of $250 monthly pays $71 in cash for a total stamp allotment of $170, thus getting a "free bonus" of $99 worth of stamps. Under the Carter plan, which has already been approved by the Senate, there would be no purchase and the family would simply get its $99 bonus.

Backers of the no-purchase plan told the House it would help millions of people who previously have not been able to afford to buy stamps to enter the program and would eliminate frauds in handling $3.2 billion worth of cash stamp sales annually.

After lively debate, the House followed its earlier precedents and slapped down, 249 to 170, a proposal by Rep. Richard Kelly (R-Fla.) to refuse stamps to strikers.

Kelly said the current practice of allowing strikers to get stamps if their incomes and assets are low enough to meet program standards puts the government on the side of unions in labor-management disputes. But Majority Leader Jim Wright (D-Tex.) countered that a stamp ban would put the government on management's side.

By a 242-to-173 roll-call vote, House members adopted an amendment by Rep. Dawson Mathis (D-Ga.) putting a ceiling of 5.8 billion on authority for stamp program appropriations in the 1978 fiscal year beginning Oct. 1. The ceiling would escalate 10 per cent a year, reaching $6.2 billion by fiscal 1981.

Critics, led by Rep. Frederick W. Richmond (D-N.Y.), said the "CAP" could force the government to cut food-stamp benefit rates in the future if unemployment suddenly increased and prospective stamp spending rose above the ceiling.

Mathis, however, said his plan was "more symbolic than anything else," partly because it is above the $5.6 billion already appropriated by Congress for the year beginning Oct. 1.

"Basically it just puts the House on record saying we want to keep some control on spending," he said. Before approving the ceiling, the House rejected a more restrictive $5.6 billion fiscal 1978 ceiling by 248 to 168.

The House voted down two amendments to ban the use of stamps for junk foods - including ice cubes and cocktail mixes - after critics said the plans owuld reduce sales of such food much but would inconvenience middle-income food shoppers by slowing down supermarket checkout lines.

House Agriculture Committee Chairman Thomas S. Foley (D-Wash.), said stamp recipients could, if tey chose, use their own cash to buy the banned foods while purchasing "approved" foods with stamps.

Administration and congressional experts estimated that 2 million to 3 million new participants would enter the program because of the free-stamp provisions, but 1.3 million present participants would be dropped and 4.4 million would get reduced benefits.