A newly formed Committee for National Security warned yesterday that the results of last week's election could "accelerate the growing militarism of this country."

Americans concerned about the economy and the perceived loss of U.S. power and prestige clearly voted for a change, but the consequences, said committee director Nancy Ramsey, could include "drastic economic costs and the heightened likelihood of war."

Though the committee describes itself as bipartisan -- and William Colby, former CIA director in the Nixon and Ford administrations, showed up to support the group at a news conference here -- its membership largely comprises former Carter administration aides and other liberal Democrats who are worried the cry for stronger defenses in the current conservative mood could go well beyond what they believe is needed.

Both Colby and Paul Warnke, former chief negotiator in U.S.-Soviet strategic arms talks for the Carter white House, acknowledged that U.S. military forces need improvement. But Warnke said the campaign debate over national security was largely bombast and the United States must avoid the view that foreign policy problems can be solved by military means or that American military strength can be improved simply "by throwing money at it."

The news conference came one day after Sen. John Tower (R-Tex.), soon to be chairman of the Senate Armed Services Committee, told reporters that higher defense spending is the top priority of the new Reagan administration. "Tower came out for every costly program" advocated by the military, Warnke said.

But each of these programs should be approved or rejected in its merits, Warnke maintained, not on a symbolic basis in which a vote against any particular weapon will somehow signal American weakness.

Warnke said the committee viewed itself as neither "hawk nor dove" but as "owls" intent on exposing the nuts and bolts of defense issues.

Colby, who supported Reagan, nevertheless cautioned against the United States putting its faith in a new "Maginot Line" of military spending when, he said, the threats to U.S. security from worldwide economic instability and flare-ups in the less-developed world may be even more serious. The United States, he said, must carefully select the right weapons for keeping the Kremlin at bay but also needs a "forward, progressive policy to overcome the sources of real turmoil, or real danger to our national security in the years ahead" in these other areas.

With the new conservative makeup of the Senate, it is possible outside groups may become more important as sources of challenge to administration defense policy. In an effort to dramatize its theme that the definition of national security should be broadened to include other measures of U.S. domestic strengths and weaknesses, other committee members taking part in yesterday's news conference included Ruben Bonilla, president of the League of United Latin American Citizens, and Linda Tarr-Whelan, a former Carter aide who is now an executive with the National Education Association.