The House Armed Services Committee has watered down this year's leading attempt to stop Pentagon officials from joining the defense contractors they have supervised, the bill's chief sponsor said.

Rep. Charles E. Bennett (D-Fla.) said the weakening amendments severely restrict the number of employes covered by the bill's civil and criminal penalties. Bennett said he plans to offer the original version when the House takes up the defense-authorization bill this week.

The dispute over the "revolving door" measure illustrates Congress' difficulty in changing defense-procurement procedures.

Bennett's original bill barred Pentagon employes from working, during the two years after they left the government, for any contractor whose work they had dealt with while working for the government. Employes who violate the law would be subject to a year in prison and a fine of $10,000. Contractors could be fined $100,000 or more.

An amendment the committee adopted last week, introduced by Rep. Floyd Spence (R-S.C.), would allow the Pentagon to exempt high-level officials from the law. Another, by Rep. Beverly B. Byron (D-Md.), would restrict the law to middle-level procurement officials to be listed by the secretary of defense.

A spokesman said Spence is concerned that some top officials "would . . . be dead in the water after they agreed to serve in a high-level position." An aide to Byron said, "You have to be careful you don't penalize honest people . . . . You might not get qualified people going into those jobs if they feel they're going to be dead-ended."

The General Accounting Office said last week that fewer than one-third of former Pentagon employes who go to work for defense contractors report their employment, as required by law.