The General Accounting Office said Thursday the government should seize control of about 350 insolvent savings and loans so they will not undermine healthy thrifts by offering unusually high interest rates.

Under government control, insolvent thrifts would be restricted to "investing in high-grade securities, managing bad assets (problem loans) on their books and accepting deposits at prevailing market rates," Comptroller General Charles Bowsher told the Senate Banking Committee.Bowsher, the GAO's director, recommended the takeover to bar crippled savings and loans from offering exorbitant interest rates to depositors and investing their money in risky real estate deals and other potentially dangerous ventures.

Failing savings institutions have often resorted to such practices to raise sorely needed funds in an effort to make substantial profits.

The tactics have contributed to the magnitude of the industry's crisis, but they have also forced healthy firms - about 2,700 of the 3,000 federally insured institutions - to pay depositors high interest rates to compete with insolvent firms.

"These institutions must be effectively isolated from the rest of the depository institutions industry to prevent them from competing with healthy institutions," Bowsher said.

Bowsher also told the committee he would like the FSLIC be made independent of the Federal Home Loan Bank Board.

Bowsher estimated it will cost the government $85 billion to meet previous commitments to rescue failing thrifts, to close or sell the remaining insolvent institutions and to provide $20 billion to replenish the fund that insures savings and loan deposits up to $100,000.