Despite rhetoric about cutting the budget and controlling inflation, House Democratic leaders took steps last week to ensure that the key Budget Committee would not slash programs too deeply.

In filling seven vacancies on the Budget Committee, the Democratic Steering and Policy Committee nominated six moderates or liberals and only one member, a Florida freshman, Rep. Bill Nelson, who could be considered conservative.

House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) denied generally that committee assignments were filled with an eye to ideology or other factors, such as who would win a key subcommittee chairmanship on Commerce.

Instead he said committee slots were filled through political wheeling and dealing among members of the Steering and Policy Committee, which consists of the Democratic leadership and 12 regionally elected Democrats.

But conservatives say they believe that the leadership, at least in the case of the Budget Committee, stacked it in favor of liberals.

One disappointed conservative, Rep. James R. Jones (D-Okla.), who was nominated by the Ways and Means Committee for the Budget Committee but turned down by the Steering Committee, is considering challenging that rejection in the Democratic Caucus next week. The Steering Committee nominations must be voted on by the Democratic Caucus.

Jones said he believes that by "stacking it with liberals" the Democrats are bringing trouble upon themselves. "We are probably going to have some pretty heavy philosophical fights among our own party" he said, adding that Democratic fiscal conservatives could join Republicans to defeat the Budget Committee's budget resolution on the House floor. Carter's budget goes to Congress Monday.

Jones claims that labor worked against him, and that a labor lobbyist has told him, "We believe the Carter budget is too tight and we don't want budget-cutters on the committee."

Of the 17 Democrats, old and new, named to the Budget Committee, one could be considered conservative and three of four moderate.

Freshman Democrats, elected in the year of Proposition 13, are expected to join the cutback chorus, and the leadership may want to protect social programs as much as it can in the commitee, in expectation of meat-cleaver attacks by both Republicans and Democrats when the budget gets to the floor.

In filling assignments to other committees, intramural politics appeared to play a heavy role.

One key question is whether the Steering and Policy Committee tried to put a tilt on the hottest chairmanship race in the house, the one between Rep. Henry A. Waxman (D-Calif.) and Rep. Richardson Preyer (D-N.C.) for chairman of the important House subcommittee on interstate and foreign commerce.

The five members nominated for Commerce Committee vacancies claim they are committed to neither Preyer nor Waxman, and Waxman, Preyer and the leadership all deny that the fight influenced the choices.

But before the Steering Committee balloting on the commerce vacancies, Waxman, who serves on the Steering Committee, and Rep. Richard Bolling (D-Mo.) got into a shouting match on the subject of Waxman's candidacy. Bolling questioned the ethics of Waxman's having raised and distributed campaign money to his colleagues on the commerce committee, and Waxman called Bolling's charges "ungentlemanly."

Waxman failed to get a fellow Californian, freshman Rep. Robert T. Matsui, nominated to the committee. And another Steering Committee member, Rep. Charles Rose (D-N.C.), told reporters he believed those nominated will help Preyer in his close race.

Texas, with the aid of Majority Leader Jim Wright (D-Tex.), did very well in getting its members on key committees, as Texans won spots on Rules, Ways and Means, Appropriations and two seats on Commerce, where oil policy will be decided.

Conversely, California failed in its attempts to get key seats on Appropriations and Commerce.