The House last night rejected the fiscal 1980 budget plan proposed by its Democratic leadership, apparently in protest over the measure's $29.3 billion deficit.

The action, which came on a vote of 213 to 192, surprised the measure's floor managers, who had been confident that the budget plan would pass.

The House now must reopen consideration of the budget resolution to try to come up with a smaller overall deficit -- a feat that may prove difficult amid conflicting pressures for increased spending.

Rep. Robert N. Giaimo (D-Conn.), chairman of the House Budget committee, who stood by helplessly last night while the proposal went down to defeat, said he was not sure when he would seek to bring the measure to the floor again.

"It beats me. I'm just going to sit on it for a while and let them stew," Giaimo told reporters after the session ended last night.

Last night's defeat was not the first time in the five-year-history of the budget process that the House has rejected a budget resolution. The lawmakers defeated the budget measure in 1977, also in protest against the deficit, and voted down a conference report last May.

Meanwhile, the Senate yesterday approved a budget plan that calls for a deficit of $31.6 billion and a full 3 percent increase in defense spending over what is needed to keep pace with inflation. The vote was 62 to 36.

The House vote was surprising because Democratic leaders had expected they could win approval of the resolution as long as they held the deficit below $30 billion.

However, the Senate's action in increasing the deficit was expected to make it more difficult for the two chambers to reach a compromise if the House finally approves a lower-red-ink figure. Glaimo said yesterday "we may be here until Christmas" before the issue is resolved.

Congress had proposed a $23 billion deficit in initial spending targets set last spring, but the House and Senate Budget committees were forced to increase that because of inflation and higher unemployment payments.

The resolution's defeat in the House came after Democratic majorities in both houses rejected GOP bids for an election-year tax cut and proposals for further across-the-board cuts in spending.

The House also refused to follow the Senate in cutting back pending appropriation bills to make up for cost-saving measures the lawmakers promised last spring but never enacted. It also voted down a conservative-backed proposal to mandate a balanced budget.

The two houses also were far apart on defense spending. The Senate's resolution calls for a full 3 percent increase in defense outlays beyond that needed to keep pace with inflation. The resolution the House had been considering yesterday would have provided for a 1.5 percent boost.

The Senate increase in defense spending was approved largely at the insistence of conservatives, who had pressed for the 3 percent rise next year -- and a 5 percent increase in fiscal 1981 and 1982 -- as a condition for supporting the SALT treaty.

The Carter administration officially had backed the 3 percent increase, but took a hands-off approach in the House partly for tactical reasons. The conference committee is expected to recommend a figure somewhere in between.

The GOP tax-cut plans were denounced in both houses as likely to fuel inflation and wreak havoc with the budget. The measures were rejected by votes of 61 to 36 in the Senate and 230 to 187 in the House.

Both measures would have cut spending sharply to offset some of the tax reductions. GOP sponsors insisted their deficit would be lower than the Democrats' because the tax cuts would spur the economy.

However, despite the temptation of a tax-cut and a lower deficit, Democratic leaders in both houses were able to prevent any significant defections. Only 39 House Democrats voted for the GOP plan.

In the Senate, Sen. Edward Kennedy (D-Mass.), who yesterday said he thought the economy might need a tax cut next year, also voted against the GOP proposal. Kennedy had opposed similar measures in previous years.

The Democrats' position on the tax cut allied them closely with President Carter, who has contended it is too early to tell whether a tax cut will be needed and has urged lawmakers to wait until January before deciding the issue.

Although the administration is predicting that the recession will worsen this year, Carter has halted any talk of a tax cut for fear it might exacerbate inflation. The president has forbidden his own advisers to discuss the issue.

The GOP tax cut proposed in the House would have slashed taxes by $20 billion and cut spending $19 billion, resulting in a deficit of $20.2 billion. The Senate plan would have trimmed taxes $24 billion and cut spending by $16.7 billion.

The major House vote to reject any further rise in defense spending came when the lawmakers killed, 221 to 191, a proposal by Rep. Samuel S. Stratton(D-N.Y.) to boost authority to commit defense monies for future years by 3 percent more than inflation and raise fiscal 1980 outlays by $400 million.

Earlier, House members also defeated a move by Rep. Eldon Rudd (R-Ariz.) that would have increased defense outlays by 5 percent over inflation next year -- outstripping the Senate action.

The budget resolution the House rejected yesterday was the second Congress has considered this year. Under the current budget law, the lawmakers must set initial spending targets each spring and then revamp them in September to establish binding ceilings.

The House budget resolution last night was opposed by four of the five Washington-area members of the House, Reps. Gladys N. Spellman (D-Md.), Marjorie Holt (R-Md.) Joseph L. Fisher (D-Va.) and Herbert S. Harris (D-Va.) Rep. Michael D. Barnes (D-Md.) voted for the measure.