House Democratic budget-drafters yesterday were considering a plan to embrace Senate-proposed tax increases in conjunction with defense spending cutbacks that could produce a lower deficit than contemplated by either the president or the Senate.

But House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) continued to insist on bipartisan support for any tax rise so that President Reagan could not blame the Democrats for it in this election year.

O'Neill and other Democratic leaders met with the budget-writers yesterday, and another session is planned before the House Budget Committee begins formal work on the fiscal 1987 budget, tentatively scheduled to start this afternoon.

At yesterday's brief session, Budget Committee Chairman William H. Gray III (D-Pa.) outlined a plan to achieve a deficit of about $10 billion less than the $144 billion required by the Gramm-Rudman-Hollings budget-control law and anticipated in the budget approved by the Senate last week.

The plan, which Gray was publicly characterizing as only an "option," would accept the Senate's plan for $13.2 billion in unspecified tax increases but use any revenues that exceed Reagan's proposal for $5.9 billion in revenue increases for deficit reductions that go beyond Gramm-Rudman-Hollings requirements.

Democrats, leery of being accused by Reagan of raising taxes to support more spending, could then claim that the excess revenues were being used for deficit reduction, which they believe is a good campaign issue for this fall.

The Democrats would also pick up budget savings from cutting far deeper into defense spending than the Republican-controlled Senate did, reducing new military spending authority from this year's $287 billion to $282 billion. The Senate agreed to increase spending authority to $301 billion, slightly more than enough to cover inflation.

The plan ran into "a lot of questions . . . concern . . . doubts" at the leadership meeting, according to one participant.

At a briefing before the session and to colleagues during the meeting, O'Neill reiterated that he wants support from House Republicans before putting Democrats on the line for a tax increase.

"I want to take from the president the idea that the Democrats are taxers and that the Democrats are spenders," he said. "We're trying to get away from that image. That's the image that hurt us in the last election," he said.

If the House can produce a bipartisan plan for tax increases, O'Neill said, "I'd buy it."

He said he expected the budget panel to include tax increases in its budget plan but added that he would bring it to the House floor "only if there are Republican votes for it."

A spokesman for House Minority Leader Robert H. Michel (R-Ill.) described Michel as "fairly rigid" against tax increases but added that "he never shuts the door on any option." His position could depend on "how the rest of the budget shapes up," the aide said.