The chairman of the Commodity Futures Trading Commission gave a House Agriculture subcommittee plans yesterday for making his agency more effective, but across Capitol Hill two convicted commodity swindlers testified that the criminal element is already one step ahead of federal regulators.

As Congress began debating whether to abolish the commodity commission, widely varying views of the agency's ability to keep the commodity business honest were voiced:

* CFTC Chairman Philip McBride Johnson laid out a legislative program that he said would answer many of the complaints raised in a critical General Accounting Office audit of his agency.

Johnson would turn some authority over commodity fraud back to state prosecutors, tighten loopholes that allow some commodity salesmen to escape federal regulation and shape up the CFTC's snarled customer-complaints system.

* A House subcommittee issued a report on the collapse of the silver market two years ago, concluding: "The 1979-1980 silver futures markets and the events associated with them indicate that the CFTC had not developed the necessary programs, procedures or policies to prevent market manipulations and conflicts of interest."

* Two convicted commodity swindlers, four con-game victims and several state regulators testified that present federal regulations not only do not stop commodity fraud, but instead prevent local authorities from prosecuting high-pressure "boiler room" operators who sell commodities by phone.

The con men, victims and state officials testified before a Senate permanent subcommittee on investigations hearing on commodity fraud while Johnson was addressing the House Agriculture subcommittee on conservation, credit and rural development.

The simultaneous subcommittee hearings made it clear the CFTC will not be routinely reauthorized as most federal agencies are.

Although there is no movement yet to shut down the agency or to merge it with the Securities and Exchange Commission, several lawmakers are urging major changes in the CFTC as a result of embarrassing disclosures about the agency's weaknesses.

The CFTC has been faulted for failing to stop outright fraud and for its inability to prevent conflicts of interest and market manipulation in the largely self-regulated markets where legitimate commodity trading is done.

Sens. William Roth Jr. (R-Del.), who chairs the Senate panel, and Warren Rudman (R-N.H.), vice chairman, said they will introduce legislation to take away CFTC's exclusive jurisdiction over commodity trading.

At present states cannot prosecute commodity crooks who are registered with the CFTC; as a result, swindlers sign up with the federal agency so they will be immune from local authorities.

The CFTC "is a good example of where President Reagan's New Federalism can be employed" to turn some authority back to states, suggested Rep. Dan Glickman (D-Kan.). Glickman said Kansas officials have complained that "the CFTC's version of investor protection is a national disgrace."

Glickman and others on the House panel offered high praise for CFTC Chairman Johnson, who took over the agency less than a year ago.

Johnson said he has declared "open season" on "frauds masquerading as commodity investments" and has called on Congress to repeal privacy restrictions that now prevent the CFTC from cooperating with state investigators.

The CFTC's legislative proposals, Johnson noted, advocate giving the states some authority over commodity fraud. The CFTC plan still would prevent states from prosecuting persons registered with the federal agency; state officials testifying at the Senate hearing said that isn't enough.

Johnson asked Congress to make changes in the CFTC reparations program, which was supposed to be a sort of "small claims court" for disputes between investors and brokers.