Needing ratification by three more states by March 1979, the Equal Rights Amendment suffered setbacks this week in two state legislatures.

A 22-to-12 vote yesterday in the Missouri Senate defeated the proposed constitutional amendment after intense parliamentary maneuvering. It was the second time in two years that the Senate has rejected the amendment, which would declare that "equality of rights under the law shall not be denied or abridged by the United States or any state on account of sex."

In Oklahoma, after weeks of intense lobbying, the amendment has apparently died without a vote.

The chief House sponsor, Rep. Charles Morgan, moved to refer the proposal back to committee on Monday, saying he did not have the votes for floor passage.

Earlier, Morgan had said he had 50 "solid" votes in favor, but last week he announced that there had been four defections. Passage would have required 51 votes in the 101-member House.

Reassignment of the proposal to committee also means it is likely to be dead for the legislative session of 1978, an election year when lawmakers are not likely to tackle the ticklish issue.

ERA has been defeated three times in the Oklahoma House, while passing the Senate once on a voice vote.

So far, 35 states have ratified the amendment. Ratification by three-fourths of the states is required by March 22, 1979.