Prosecutors on Monday demanded a 20-year jail sentence for a left-leaning lawmaker accused of plotting an armed rebellion against the government.    

Rep. Lee Seok-ki of the minor opposition Unified Progressive Party (UPP) went on trial in September on charges of conspiring with members of a clandestine organization to topple the Seoul government if a war with North Korea broke out and instigating them to do so.

In February, a local court sentenced him to 12 years in prison and stripped him of his civic rights, such as suffrage, for 10 years following his eventual release from prison.

"Considering that the accused prepared a rebellion in detail through the revolutionary organization named RO that defines the Republic of Korea as its enemy, the original 12-year sentence is too light for him," a prosecutor in charge of the case told the Seoul High Court.

The prosecution previously demanded the same 20-year sentence during the first trial.

At the appeals trial, prosecutors explained in detail about the revolutionary organization and its activities as well as the dangerousness of the alleged rebellion plot.

"The RO, during a meeting in May last year, discussed in detail about how to acquire firearms and bombs and blow up railways, communication lines, gas lines and roads," the prosecutor told the court. "We request that the court apply the maximum penalty for the crime, which could have caused huge human losses and social chaos."

Lee, a former student activist, was elected to the National Assembly on a proportional representation ticket in the 2012 general elections.

The sentencing trial is scheduled for Aug. 11. (Yonhap)