Amnesty International today accused the Colombian government, which is engaged in tense negotiations with guerrillas holding 18 diplomats hostage, of permitting political prisoners to be "systematically tortured in military installations."

The London-based organization, winner of the Nobel Peace Prize in 1977, took the unusual step of releasing its recommendations despite an appeal from Bogota that the findings remain secret at this delicate stage in the 51-day hostage crisis.

A member of the three-man mission that visited Colombia in January at the invitation of President Julio Cesar Turbay Ayala said the recommendations were released in advance "because the situation is so bad. Colombia is a major human rights violator."

Anmesty's two major recommendations were that Colombia lift the state of siege in force almost constantly for the past 30 years and end "judgment of civilians in military courts." Although Colombia is one of South America's few democracies, the military has sweeping power to maintain order.

The M19 left-wing guerrilla group holding the diplomats, including U.S. Ambassador Diego Asencio, has charged repeatedly that its members are tortured while imprisoned arbitrarily. The guerrillas initially demanded release of about 300 prisoners in exchange for the hostages captured during a reception at the Dominican Republic Embassy.

Colombia has refused to free prisoners but has sought to facilitate trials of some accused guerrillas. One court case began this week in a military process of the type denounced by Amnesty Interntional.

In the face of outside criticism, Colombia has invited observers to such trials and a staff team from the Inter-American Commission on Human Rights here left yesterday for Bogota.

However, Amnesty said that its inquiries about attending the trials were met by a cable from Turbay saying no such blanket ivitation had been issued. The Amnesty team made its survey before the capture of the hostages but after a wide-ranging national debate about the methods used in a massive roundup of suspected guerrillas following several attacks against the military.

The report said Amnesty "appreciates the difficult problems of public order that the Colombian government confronts, especially those caused by the violent action of armed groups or revolutionary movements, but the political imprisonment that exists in Colombia has gone beyond the limits of countering violent opposition and many of those arrested were exercising their human rights in a nonviolent way.

"In many cases, those arrests have been accompanied by torture."

The mission named 33 centers where it charged that torture regularly occurred, from beatings and electric shock to use of drugs.

The mission also charged that "arbitrary arrests, ill treatment and assassination of peasants and rural Indians" occur in rural and tribal areas ultimately under military authority.

Members to the Amnesty mission included Spanish law professor Antonio Carretero Perez, psychiatrist Federico Allodi of the Canadian Amnesty group and Edmundo Garcia of the group's office in London. The member characterizing Colombia as "a major violator" refused to be identified by name.

Amnesty said in a press release that it "decided to make the mission's recommendations public to end rumors and speculation in the Latin American news media about them." The 4-page findings were submitted to the Colombia government April 1.

United Press International reported from Bogota that a radio station there had the complete document and had broadcast its findings.