Cocaine and other illegal drugs are costing the nation tens of billions of dollars a year in lost wages, law enforcement expenses and treatment, according to a new congressional report. But no price tag exists for what are generally believed to be the enormous costs to society created by the family strife, suicide and violence that drugs produce, the report said.

Purer, cheaper and more easily attainable cocaine and heroin, as well as "designer drugs" produced in clandestine labs, have altered the shape of drug abuse in the 1980s, according to the study by the General Accounting Office, the investigative arm of Congress. Regarded as the entry-level to drug abuse, marijuana is still the most widely used illegal drug in the country, and although its use has declined since the 1970s, its potency has increased, the report said.

The GAO report -- which focused in part on the increase in drug overdose deaths in the District, as well as increases in the use of cocaine and PCP in the city -- is the latest in a series of indicators of the scope and seriousness of the drug crisis in America. Last week, a Rand Corp. report said that Washington and its suburbs appeared to have the worst drug problem among 27 of the nation's largest cities.

The release of the GAO report yesterday was timed to coincide with the White House Conference for a Drug Free America, a national forum of about 2,500 drug abuse specialists, government officials and former addicts meeting here this week and charged with recommending solutions to unprecedented drug abuse. It also came on a day in which some members of Congress expressed growing dissatisfaction with President Reagan's drug enforcement and prevention efforts.

Seven congressmen yesterday blasted the Reagan administration for failing to have a national policy to combat rising drug use, violence and trafficking, particularly the importation of narcotics from Latin nations receiving U.S. aid.

Rep. Charles Rangel (D-N.Y), chairman of the House Select Committee on Narcotics Abuse and Control, told the White House conferees that Americans spent about $140 billion last year to buy 178 tons of cocaine, 12 tons of heroin and about 60,000 tons of marijuana. He called on the administration to help local police combat drug violence, develop treatment and prevention programs and halt aid to nations such as Panama, Colombia and Mexico that export narcotics.

President Reagan told Congress yesterday that Panama and three other nations had not been cooperative with U.S. efforts to halt drug trafficking and are liable for sanctions. He certified as cooperative and eligible for continued aid 17 other countries, including Mexico and Colombia.

"It's tragic for anyone to believe that we are winning this battle against drugs when we haven't fired the first shot," Rangel said to applause at the White House conference.

"We have no domestic or foreign policy on drugs. If you want to fight this war, you have to put up the resources for the boys in the front lines," he said.

"We hope that we'll be able to set a national policy. That is our purpose here. Our charge is to set a national policy -- that is my response to Congressman Rangel," said Lois H. Herrington, chairman of the conference mandated by the Anti-Drug Abuse Act of 1986. Divided into 10 working committees with topics such as law enforcement, abuse prevention and treatment, the conferees will submit a final report and propose solutions to the president and Congress next summer.

The GAO, Rand and other recent reports and crime statistics have portrayed the United States as a nation deep in a drug crisis. "Cocaine has emerged as the widely abused drug of greatest concern," said the GAO report, "Controlling Drug Abuse: A Status Report." Among its other findings:

In 1983, the latest year for which figures are available, drugs cost the nation about $60 billion in lost employment, prison and other criminal justice expenses, and treatment programs.

The number of cocaine-related emergencies reported by hospitals jumped 167 percent from 1983 to 1986.

The number of annual cocaine-related deaths rose from 328 to 734, or 124 percent, between 1983 and 1986, an upward trend that continued in the first six months of last year.

The average street-level purity of cocaine more than doubled from 1981 to 1986, from less than 30 percent to nearly 60 percent. At the same time, prices declined, signaling increased availability.

The number of people who had used cocaine remained about the same from 1982 to 1985, increasing slightly from 21.6 million to 22.2 million. But the number of Americans over age 12 who were current users increased 38 percent during the same period, from 4.2 million to 5.8 million.

About 62 million people over age 12 have used marijuana at least once and 18 million currently use it, compared with 56 million who had used it at least once and 20 million who were using it in 1982. Current use among high school seniors declined from 34 percent in 1980 to 21 percent last year.