Budget director David A. Stockman, attending to head off a counteroffensive by House Speaker Thomas P. O'Neill Jr. (D-Mass.), said yesterday that Congress will be guilty of "deliberate sabotage" if it reneges on spending cuts it proposed just last month.

In a briefing for reporters as Congress gears up for the second round of its budget battle, Stockman left little doubt that the administration will keep up the heavy lobbying pressure that helped give President Reagan a clear victory in the first round.

In round one, Congress ordered its committees to come up with more than $35 billion in program cuts to accommodate a slashed-back spending program of $695.5 billion for fiscal 1982. The committees are supposed to propose their specific cuts by June 12, and the House and Senate Budget committees are then required to package the results into a bill for enactment by the two houses.

But O'Neill, who strongly opposes many of the proposed cuts in social welfare programs, has invited the committees to prepare amendments for restoration of some of the money and signaled that he wants the Rules Committee, which has jurisdiction and control over the procedures, to permit separate votes on at least some of the amendments.

Without mentioning O'Neill by name, Stockman contended that the administration was "flexible on details" but would consider any "major deviation" from the blueprint that Congress adopted last month as tantamount to a "deliberate sabotage of the expressed will of Congress and the American people."

Moreover, he said the administration will be watching closely for any "creative accounting and dishonest scorekeeping" as the committees attempt to meet the targets for cuts that Congress set out in its first budget resolution that was finally adopted on May 21.

Implicitly disputing O'Neill's contention that Congress should be allowed second thoughts on massive reductions in major programs it has adopted over the years, Stockman insisted that Congress made all the necessary policy decisions in its votes last month and should now ratify them in an omnibus bill without amendments.

O'Neill has already suggested amendments for college loans and school lunches, but Stockman said that even one or two amendments would be risky because it would "open the door" to even more whittling away at the package.

Some form of so-called "closed rule," under which few if any amendments could be offered on the House floor when the spending cut package is considered, is "absolutely essential," Stockman said.

He said it was also essential that the Budget Committee be allowed to fill the gap if one or more committees fail to meet the established targets for cuts. House Budget Committee Chairman James R. Jones (D-Okla.) has already said the committee will prepare and push any amendments necessary to do this.

Although some House members, including Republicans, said that Reagan got their votes initially on the budget by indicating it was not locked in concrete, Stockman said any retreat now would be inconsistent with policy decisions that have already been made. Even many Democrats are insisting that the policy be maintained, even if some of their leaders think otherwise, he added.

Responding to Stockman, O'Neill said the House "ought to have an opportunity to vote on some of the items" in the spending cut package. "This is a democratic body," the Speaker added.