Three federal agencies accused the Commodity Futures Trading Commission yesterday of allowing trading in "exotic" futures contracts to grow too fast.

The rapid expansion of futures trading in government bonds, home mortgages and other financial instruments was criticized at congressional hearing by high-level spokesmen for the Securities and Exchange Commission, the Federal Reserve Board and Treasury Department.

All three agencies have carried on a running fight with the CFTC over how and by whom financial futures markets are regulated, and yesterday they took their case to the house subcommittee that oversees commodity futures trading.

The CFTC is unable to adequately regulate the exploding financial business, the Treasury, Fed and SEC officials complained. Commodity regulators have not done enough to protect investors and to assure that financial futures markets are not manipulaged by unscrupulous speculators, they charged.

CFTC officials had little oportunity to defend the agency because none of the complaints came up while CFTC Chairman James Stone was testifying before the subcommittee on conservation and credit.

Unlike most commodity futures, which allow investors to buy contracts for future delivery of corn, wheat or other farm products, financial futures are contracts for future delivery of financial instuments -- Treasury bills, mortgages, etc.

Since the idea was first accepted by the CFTC a couple of years ago, 13 financial futures contracts have been created, although several of them have failed to develop much interest among investors.

Stone assured the subcommittee that the CFTC is not rushing to approve the most controversial financial futures contract of them all -- one based on a stock market index, such as the Dow Jones Industrial Average.

The Kansas City Board of Trade already has applied to start trading in futures based on the Value Line Stock Index. Other markets are preparing their own versions, based on other Wall Street fever thermometers.

The federal Reserve requires investors to put up 50 percent of the price of stock in cash, but most commodity futures contracts require a down payment of only about 10 percent. Raising that to 50 percent would make stock index futures far less attractive to investors.

SEC General Counsel Ralph Ferrara says his agency believes the same regulations that apply to sale of any stock should apply to sales of stock index futures. The SEC's disclosureregulation and its rules to protect investors are tougher than those of the CFTC, he added.

Robert Carswell, deputy secretary of the Treasury, urged Congress to consider "whether the CFTC's resources are adequate" to regulate futures trading in Treasury bills and other government securities.

Peter Keir, assistant to the Federal Reserve Board, also urged curbs on financial futures markets.Much of the trading, he said, "appears to be designed largely to facilitate interest rate speculation, and a growing share of activity appears to reflect tax avoidance objectives."