At a plenum of the Central Committee held on 11 and 12 June 1949, Vasil Kolarov delivered an indictment of Kostov's anti-Party activity.
Kostov was sentenced to death on the grounds that he had organized the headquarters of an underground organization aiming to overthrow the government by violence, had committed actions aiming at the worsening of the friendly relations between Bulgaria and the Soviet Union and the other people's democracies, had placed himself under the orders of the British, American and Yugoslav intelligence services for espionage, that while fulfilling state duties and instructions before foreign governments he had deliberately performed his services and carried out his instructions to the detriment of the state and he had committed acts aiming at the disorganization of the national economy and the supply system of the country and that he had close political connections with Tito, who had broken with Stalin.
The other 10 accused prominent Communists, among them ministers and high Party officials, received life imprisonment, 15 or 12 years sentences.
During the preparation of these staged trials most inhuman types of interrogation methods were used and more than 30 prominent Communists were sentenced to long term imprisonment.
On 11 April 1956, at a Sofia City Communist Party meeting it was stated that: a harmful consequence of the personality cult had been the infringement of the laws, as a result of which innocent people were unjustly accused and sentenced.
The trial of Kostov is mentioned in passing in chapter 3 of In the First Circle by Aleksandr Solzhenitsyn, as a "crude judicial farce" followed by a "sham recantation, allegedly written by Kostov," which Lev Rubin is ashamed to mention to his German fellow-prisoners on Christmas Eve when they ask him for information on recent events in the news.