The leader of New York's Liberal Party said yesterday he expects the party's policy committee to recommend an endorsement of independent presidential candidate John B. Anderson today, a move many Democrats fear could lead to President Carter losing the Empire State's 41 electoral votes.

Liberal Party leader Raymond B. Harding said the 36-member committee will meet today with Anderson and his vice presidential running mate, Patrick J. Lucey, "and thereafter they will make a recommendation."

Asked if he anticipates the committee would recommend an Anderson endorsement, Harding said: "That's the way it appears to be going. Yes.

Meanwhile, in a move that could significantly enrich the Anderson treasury, Anderson campaign officials filed a federal court suit yesterday asking that their National Unity Campaign be treated as a national political party, with the same contribution and spending limits as the Democratic and Republican national committees.

This could greatly increase Anderson's ability to raise funds, since individuals may legally contribute $20,000 to national political parties, while they are limited to contributions of just $1,000 each to a presidential candidate's campaign. Political parties can also spend $4.7 million on a general election campaign in addition to the spending limits of individual candidates.

Anderson had maintained previously that he was a truly independent candidate and that his National Unity Campaign was not a separate party. Yesterday, Mitchell Rogovin, Anderson's chief lawyer, said that technically Anderson is still maintaining that his campaign is not a separate political party. It just wants to be judged by the same rules as the major political parties, he said.

"It comes down to this: I'm not a duck, but I waddle and swim and I have feathers -- and so, if you want to call me a duck, then it's okay with me," Rogovin said.

If the New York Liberal Party's policy group approves an endorsement of Anderson, the recommendation would then go to the party's 300-member state committee which is scheduled to meet Sept. 13 for formal action.

If Anderson is endorsed, it would be the first time in the Liberal Party's 36-year history that it has not endorsed the Democratic nominee for president.

The party, however, has played an influential role in electing a host of liberal Republicans in New York City and state, including former mayor John V. Lindsay, the late Nelson A. Rockefeller and Sen. Jacob K. Javits.

Lt. Gov. Mario Cuomo, who heads Carter's New York campaign, described the potential impact of the endorsement this way: "When you think that if the Liberal Party would have endorsed Eugene McCarthy in 1976, Gerald Ford would be president today, it is pretty important . . . It's clear the party could throw New York to Ronald Reagan."

With the Liberal endorsement in 1976, Carter carried New York, the nation's second most populous state, by 288,000 votes, 145,000 of which he received from Liberal Party voters.

Anderson is already splintering the Democratic vote in New York, and severely damaging Carter, according to a poll published yesterday in The New York Times. The statewide survey reported Carter leading Reagan, the Republican nominee, by 33 to 30 percent among likely voters. Anderson, showing particular strength among Jewish voters, had 20 percent.