PANAMA CITY, JUNE 16 -- The government-controlled National Assembly decreed last night that nine opposition political leaders, including a former president, and prominent businessmen had committed "high treason" during a week of protests against military strongman Gen. Manuel Antonio Noriega by conspiring to overthrow the government.

Among those declared "traitors" is former president Nicolas Ardito Barletta. Ardito Barletta said last week that Noriega forced him out of office in 1985 after he demanded an investigation of the murder of Hugo Spadafora, a popular Noriega critic who was found beheaded.

Ricardo Arias Calderon, head of the opposition Christian Democratic Party, was named in the decree.

Also included was entrepreneur Gabriel Lewis Galindo, a former ambassador to Washington who fled Panama Saturday after allegedly receiving threats from the military.

The decree is not legally binding, but could lead to arrests if the government pursues it. The charges appear to be a counterpunch by the government to allegations by Noriega's former second-in-command, Col. Roberto Diaz Herrera, that the Defense Forces chief was involved in assassination and electoral fraud. Diaz's charges sparked the week-long crisis.

Other businessmen named in the decree included Federico Humbert, a top officer of the Banco General, the largest Panamanian bank; Roberto Motta, president of the Banco Continental; Fernando Eleta, owner of a Panamanian television station; and Roberto Aleman, president of the national brewery and another former ambassador to the United States.

The businessmen were believed to have been in touch with Lewis last week while he conducted a failed mediation between Noriega's Defense Forces and the opposition.

The assembly charged that the businessmen tried to impose a government that would allow the United States to retain the Panama Canal after the year 2000, when, by treaty, it will be taken over by Panama.