Dozens of people went on trial Saturday in Tehran, accused of rioting and threatening to overthrow the Iranian government.
The court appearances stem from the mass protests that followed the country's disputed election results in June.
Those on trial included a French citizen and an Iranian national employed as a political analyst at the British Embassy in Tehran.
Among those seated in the front row of the Revolutionary Court was 23-year-old French academic Clotilde Reiss, who was reportedly arrested July 1 at the Tehran airport. She wore a scarf over her hair and sat beside a police officer.
"Families are saying this is completely a show trial," a freelance reporter in Tehran told CBC News, which is not identifying him because journalists are at constant risk of government interference and arrest in Iran.
"What the government wants from the prisoners is forced confessions that they can show on state-run TV and say that what has happened in Tehran was plotted by foreign countries," the journalist said.
The government has repeatedly accused Britain and the United States of using the pro-reform movement as a tool to spark a revolution to topple Iran's Islamic theocracy.
'Families are saying this is completely a show trial' —Freelance journalist in Tehran
During the court session, a prosecutor read out an indictment saying Britain and the U.S. had plans to foment unrest with the aim of toppling Iran's rulers through a "soft overthrow," the state-run Islamic Republic News Agency reported.
The Foreign Office in London, reacting to the court appearance of British Embassy worker Hossein Rassam, said his trial was an "outrage" and "completely unacceptable."
"We deplore these trials and the so-called confessions of prisoners who have been denied their basic human rights," the Foreign Office said in a statement.
Saturday's hearing was the second in a trial that started a week ago, although it was a new group of defendants facing the judge.
Human rights groups and Iran's opposition have criticized the trial as a sham and said televised confessions from defendants were scripted by authorities and extracted through pressure.
Rassam told the court that Britain was involved in the unrest, according the Islamic Republic News Agency. He said a budget of £300,000 had been allocated to establish contacts with Iranian political groups, influential individuals and activists, the news agency reported.
The news agency quoted him as saying that he personally established contacts before the election with the campaign headquarters of Mir Hossein Mousavi, the pro-reform candidate who says he was robbed of victory.