President Reagan's proposal to embark on a vast civil defense effort has failed its first big political test as the Senate Armed Services Committee refused to approve anything but modest growth in the program.

Chairman John G. Tower (R-Tex.) said yesterday that his committee agreed, in marking up the Pentagon's procurement bill, that 5 percent growth, after inflation, was adequate from fiscal 1982 to 1983 even though Reagan had recommended a much bigger increase.

Almost every senator attending the committee's closed-door sessions contended that there was no way to protect civilians from an all-out nuclear attack and that to try to do so would be a waste of money. Several also warned that to undertake such preparations would only fuel the movement here and abroad against further deployment of nuclear weapons.

Tower, sources said, was among those who argued that the best-laid evacuation plans could be blown up by dropping a nuclear weapon on the equivalent of the 14th Street Bridge.

At a news conference yesterday, Tower said the committee, in reducing Reagan's civil defense request for fiscal 1983 from $252 million to $144 million, knew that the president planned to embark on a massive program costing $4.2 billion over seven years.

The government's Federal Emergency Management Agency is assuming, for planning purposes, that the United States would have at least a week's warning of a nuclear attack and could move people from 380 "high-risk areas" to an unspecified number of "host areas" designated by the states, where they could find shelter against deadly radioactive fallout.

The Armed Services Committee's refusal to launch a big civil defense program is the third big change the normally supportive panel has made in the president's strategic blueprint.

Earlier it refused to approve $715 million Reagan requested to prepare Minuteman ballistic missile silos to hold the bigger MX missile on a temporary basis, and $1.4 billion to buy the first nine MX missiles. That $1.4 billion could be requested again once Reagan decides where the MX will be based permanently.

Tower predicted yesterday that the administration will opt for a deceptive basing mode for the MX, with a thin layer of protective anti-ballistic missiles.

James P. Wade Jr., a deputy undersecretary of defense, told the Senate subcommittee on defense appropriations on Wednesday that deployment of the MX would be delayed beyond 1986 if Congress refused to approve temporary basing in Minuteman silos.

The third major alteration the Armed Services Committee has made in the president's program is its insistence that Titan missiles be kept in service rather than retired, as Reagan recommended.

The prevailing argument within the committee was that it is inconsistent for Reagan to decry the Soviet lead in megatonnage and then recommend scrapping the U.S. megatonnage provided by the 52 Titan missiles now on the line. The committee added $74 million to maintain the old liquid-fueled missiles.

In an action sure to be contested on the Senate floor, the committee authorized $54 million to begin producing nerve gas at the Pine Bluff, Ark., plant for binary munitions.

All told, Tower said, the committee on a 16-to-1 vote with Sen. Carl Levin (D-Mich.) dissenting authorized $180.2 billion for fiscal 1983 to develop and produce weapons and run ships and planes. This budget authority total is $3.2 billion less than Reagan requested.

Committee staff workers told senators Wednesday night that the reduction would come to $2.8 billion, as reported in yesterday's Washington Post, but revised their estimate upward after more detailed computations of the additions and subtractions to the procurement bill.