President Bush picked a familiar and convenient target this week when he blamed the Democrats in Congress for the burgeoning federal budget deficit.

But by attacking "internal congressional conflicts and a committee system that is so complex that . . . nearly all budget decisions are being finessed," Bush was battling centuries-old tendencies in Congress. Further, the "spending bills that would bust the budget" Bush carped about have been passed with strong GOP support -- and include projects benefiting Republican lawmakers.

Congressional spending habits have long been a favorite whipping boy for presidents, lawmakers and congressional aides alike. President Reagan decried the budget process as "a sorry spectacle."

Stephen E. Bell, a former GOP staff director of the Senate Budget Committee, once likened the process to a "pagan cult" with "interpreters and high priests and their helpers and various incantations they mumble at appropriate times. . . . Meanwhile, most members of the Congress, and certainly almost every American outside the Beltway, have absolutely no idea what we are talking about."

But congressional budget-writing in an era of deficit reduction is complex because it involves complicated decisions about getting more revenue from taxpayers and giving less federal largess in the form of government programs -- two actions that run counter to politicians' natural inclinations.

And Congress was never meant to be a smoothly functioning institution. James Madison purposely built inefficiencies into the system to protect against rash decisions.

It is further complicated by the decentralization of power resulting from the reforms of the 1970s. House Speaker Thomas S. Foley (D-Wash.) says running the House is now a process of consensus, not edicts. The oft-quoted adage of one of Foley's predecessors, the late Sam Rayburn (D-Tex.), that lawmakers should "go along to get along" has been replaced by "every man for himself."

Bush's complaint that lawmakers are approving spending bills even before a budget agreement is reached struck some on Capitol Hill as ironic. It is, after all, the complaint of another president that makes congressional leaders determined to pass the 13 measures funding the government before the new fiscal year begins on Oct. 1. They are haunted by the melodramatic sight of Reagan dropping a huge omnibus spending bill, known as a continuing resolution, on the speaker's rostrum during a State of the Union address.

"There was not agreement that we'd put the place on hold and not do our business," said House Budget Committee Chairman Leon E. Panetta (D-Calif.).

In addition, Republican fingerprints are prominent on the spending bills that Bush said would "bust the budget." Virtually all of the 10 measures that have passed the House -- at levels that exceed Bush's budget requests by a total of $13 billion -- have had strong GOP support. And amendments to pare the measures across-the-board have been beaten back with strong support from both sides of the aisle.

In June, for example, the House voted 355 to 59 to approve a measure that would spend $20.8 billion on energy and water projects, $575 million more than the president requested. A majority of Republicans voted for the bill and GOP lawmakers provided the margin of defeat for an amendment offered by Rep. Timothy J. Penny (D-Minn.) that would have cut all discretionary accounts in the bill by 2 percent.

Democrats may control Congress, but not all of the special provisions in the spending bills go to their districts.

For example, Rep. Robert S. Walker (R-Pa.), a frequent critic of Democrats' spending practices, won a $479,000 provision that would benefit Lebanon, Pa., in the spending bill covering veterans, housing and urban development programs.

Sen. Don Nickles (R-Okla.), who sought in the Senate Budget Committee to limit fiscal 1991 spending to current levels, requested $975,000 in the Senate's version of the energy and water spending bill to repair a Tulsa levee. The Senate Appropriations Committee approved the request after Chairman Robert C. Byrd (D-W.Va.) noted that the funding might not have been available had Nickles prevailed in the Budget Committee.

Further, the spending bills cover barely half, $686 billion, of the $1.39 trillion fiscal 1991 budget. Of that amount, $492 billion is controlled by lawmakers while $193 billion is for such programs as Medicaid, for which spending is dictated by permanent law. The rest finances such mandatory programs as Social Security that are not covered by the appropriations process.

Bush's complaints about internecine struggles between congressional committees and turf battles between powerful chairmen is nothing new -- and somewhat surprising coming from a former House member who served under legendary Ways and Means Committee chairman Wilbur D. Mills (D-Ark.).

The power of committee chairmen has complicated deficit-reduction efforts. Attempts over the past few years to raise revenue by increasing Coast Guard fees and by auctioning radio frequencies, for instance, have not been able to overcome the opposition of Senate Commerce Committee Chairman Ernest F. Hollings (D-S.C.).

Last year's budget agreement between the Bush administration and Congress was severely criticized by lawmakers because the chairmen and ranking Republicans on the House and Senate Budget committees and then-House Majority Leader Foley were the only lawmakers involved. The bitterest complaints came from members of the House and Senate Appropriations committees, who protested that their spending decisions were being dictated by an agreement to which they were not a party.

In hopes of avoiding those problems this year, the bargaining teams were expanded to include the spending and taxing committees. In addition, the chairmen and ranking GOP members of committees that oversee programs likely to be targeted for spending cuts were invited to discuss their areas of jurisdiction.

But already, House Appropriations Committee Chairman Jamie L. Whitten (D-Miss.), the senior member of Congress, has taken the floor in the budget talks -- he is the only participant who stands to speak -- to complain that the whole process is an encroachment upon his panel's prerogatives, according to participants.

In meetings of the Democratic bargainers, Whitten has often complained about what he considers to be "instructions" from Panetta to other committee chairmen. Once, while voicing similar grievances, Byrd mistakenly called Leon Panetta "Leo."

Critics also point to the fact that the federal budget deficit has consistently been higher than the figure that has been projected by Congress's budget. In the last two fiscal years, for example, the spending plan adopted by Congress envisioned a shortfall of $135.3 billion. When fiscal 1989 ended last Sept. 30, the actual deficit was $152.1 billion, $16.8 billion higher.

But the difference, according to the Congressional Budget Office, was largely attributable to two unanticipated pieces of legislation: the $3.8 billion drought relief measure for farmers and the $10.3 billion down payment on the savings and loan cleanup.

Bush and his budget director, Richard G. Darman, are seeking such process changes as a line-item veto and a constitutional amendment to reform the system. Some lawmakers, though, say the fault lies not in the process, but in the participants. "I've never known of a process change that substituted for the guts and the political will to make the tough choices," said Panetta.