A major attack on the 1968 Gun Control Act was launched yesterday by senators who charged that it has "created crime from otherwise . . .innocent acts and created a whole class of criminals from the body of our citizenry."

Sen. James A. McClure (R-Idaho), who helped draft legislation to amend the law, testified before the Senate Judiciary Committee that the law has "created a grim enforcement history of abuses to the rights of American citizens. The abuses are legion . . . . "

The target of most of the criticism was the Bureau of Alcohol, Tobacco and Firearms, which enforces the nation's firearms laws.

The Treasury Department announced plans earlier this year to disband ATF and give its functions to the Secret Service and the U.S. Customs Service.

Representatives of ATF were not invited to testify yesterday, but the committee heard from half a dozen witnesses who told horror stories about alleged harassment from the agency.

Richard Boulin, of Monrovia, Md., a former policeman convicted of illegally selling seven guns from his private collection, said the case "has made my life miserable. In no way did I ever intend to violate a law."

Boulin, who is appealing his conviction, told the panel he has lost "his entire life's savings" since his 1977 arrest by ATF agents. He said the incident has cost him $100,000, including legal fees, lost salary and the seizure of his collection of 89 guns.

ATF officials have said previously that the allegations of harassment are years old and precede efforts begun by the agency in 1978 to put an end to any such tactics against gun dealers and owners.

The bill before the Senate committee and identical legislation in the House would amend the law, enacted in the aftermath of the assassinations of the Rev. Martin Luther King Jr. and Sen. Robert F. Kennedy (D-N.Y.).

The law requires licensing of gun dealers and proof of identification by purchasers, and puts restrictions on sales to convicted felons and those who have been adjudicated as alcoholics or mental incompetents.

Under the proposed Firearm Owner Protection Act, prosecutors would be required to show that alleged violators intended to break the law.

The bill would severely limit federal control of gun dealers and would end the ban on transfer of firearms between states.

Critics say the bill would make it easier for convicted felons to purchase guns by shifting to the government the burden of proving that individuals should be barred from buying them.

The measure has 58 co-sponsors in the Senate and is expected to pass easily. It has 169 co-sponsors in the House, but is expected to run into problems from Judiciary Chairman Peter W. Rodino Jr. (D-N.J.), a strong gun control advocate.

Sen. Charles E. Grassley (R-Iowa), who presided at yesterday's hearing, said the 1968 law is oppressive. "A gun does not create crime. People create crime," he said.

FBI statistics indicate that handguns were used in half of the 21,860 murders recorded last year.