The House of Delegates gave final approval to Maryland's $7.5 billion budget for fiscal 1986 tonight, hours after House and Senate conferees resolved their differences over key items.

The rapid agreement came over the angry objections of one legislator who said General Assembly leaders had made a "charade" of the process by working out the major issues in secret.

State Sen. John Cade (R-Anne Arundel), a member of the Budget and Taxation Committee who has participated in the budget negotiations for the last three years, refused to return to a scheduled conference committee meeting and vowed to fight the agreement on the floor after the chairman of his committee handed him a two-page "Budget Proposal."

The proposal, worked out between the chairmen of the House and Senate appropriations committees, the Senate president and speaker of the House at an early morning meeting, cut about $13.2 million from the budget and resolved the major items separating the House and Senate. It was unanimously adopted by the five remaining conferees after scant debate, and was approved by the full House tonight by a vote of 121 to 9.

The budget, as agreed to by the conferees, includes a compromise over the disposition of a $9 million surplus in an appropriation for employe health insurance.

The conferees also restored Gov. Harry Hughes' $5.8 million supplemental budget that was initially rejected by the Senate. The supplement includes $1.6 million in aid for Baltimore police along with an increase for welfare recipients.

The Senate will take up the budget on Saturday, and Cade, who refused to sign the conference report, said he would take the unusual action of fighting his committee on the floor. "Between yesterday and today the leadership constituted their own conference committee," said Cade at an impromptu press conference in the State House basement minutes after he left his fellow conferees.

"It's reminiscent of the Kremlin," said Cade. "It was done unlawfully, it was done illegally. It's a ripoff . . . . We're supposed to be running government out in the open and we're not doing it."

State Sen. Laurence Levitan (D-Montgomery), chairman of the Budget and Taxation Committee and the three-member Senate conference panel, said he didn't bother to tell Cade about the early morning meeting. "This isn't the first time we've done that," he said. "At times the chairmen get together with the speaker and the president to resolve some of the issues that seem to be non-negotiable."

Levitan said the compromise is merely a "proposal" to the conference commitee and his colleagues are free to reject it. The third member of the panel, State Sen. Clarence Blount (D-Baltimore City) said he had no objections to Levitan's private negotiations.

The three conferees from the House, including House Minority Leader Robert Neall (R-Anne Arundel) said they had been kept fully informed about their chairman's negotiations on their behalf and supported his efforts.

The angry interchange between Cade and Levitan came after the two clashed in the Senate lounge over an agreement on an appropriation for an addition to the University of Maryland hospital in Baltimore that Levitan had also worked out privately with the governor and House leaders. That agreement guaranteed the hospital $31 million over two years to build a shock trauma unit.

Cade, along with Sen. John C. Coolahan (D-Baltimore County) criticized Levitan with expletive-punctuated speech for negotiating the agreement without consulting the rest of the Budget and Taxation Committee and for "caving in" to the House. He also questioned the legality of guaranteeing an appropriation a year in advance.