After weeks of fancy footwork, the Maryland General Assembly managed yesterday to give itself a 48 percent pay raise over the next four years in a way that allows most legislators to tell their constituents they did not vote for the raise.

By rejecting the last of more than a dozen proposals, the House of Delegates removed the final roadblock to increasing the present legislative salaries of $12,500 to $16,000 next year, and raising them annually until they reach $18,5000 in 1982.

The last proposal, which fell 12 votes short of passage after nearly an hour of debate in the House, came in the form of a Senate resolution that would have raised the salaries to $16,000 in the coming year and frozen them at that level

According to state law, the new pay raises, which were recommended by the General Assembly Compensation Commission, automatically go into effect next year since the legislature did not vote to reduce or reject the proposals during the present session.

The salaries are intended to compensate the legislators for their work during the 90-day session.Most of them hold jobs during the rest of the year although most legislators say their legislative work is full time.

The conditions laid down by the compensation commission made it possible for legislators to guarantee themselves the full pay raise without actually voting for it, an approach taken by the House during its two sessions on the issue.

"The ones I'm mad at are those who voted against (the pay raise) and got it anyway," said Del. Daniel J. Minnick, Jr. (D-Baltimore County).

During the first consideration of the pay raise last month, the House rejected 11 proposals to freeze the salary at its present level or limit the pay raise. A motion to approve the commission report failed by seven votes.

The commission's pay recommendation then went to the Senate, which voted to limit the pay increase for both senators and delegates to $16,000. But several lawmakers said the upper chamber was merely passing the buck back to the House, which had already shown a preference for the full pay raise.

Yesterday's vote in the House rejecting alternative proposals to the commission's recommendation in effect backed both the House and Senate into getting the full raise.

The showdown vote in the House yesterday on the, Senate proposal found opponents of any pay raise in the same camp as the proponents of a full increase.

"I think I'm worth $18,500," declared Del. Robert A. Jacques (D.Montgomery County), who voted against the Senate proposal. "We each much judge the input, the labor and the dedication we bring to the job."

Del. Harold L. Bachman (D. Anne Arundel), who favored holding he salary at $12,500, said he disagreed with the argument that better salary means more qualified people.

"You had a president making $75,000," Bachman said. "Now the president make $200,000 and one almost went to jail and the one in there now should go to jail."