Samsung Electronics Vice Chairman Jay Y. Lee fought back tears and denied wrongdoing on Monday as prosecutors sought a 12-year jail term on charges that include bribing the former president to help cement control of the South Korean tech giant.

Lee, the de facto leader of one of Asia's largest conglomerates, has been in detention since February on trial for charges ranging from embezzlement to perjury, in a scandal that gripped the country for months and led to the ouster of former president Park Geun-hye.

He will face the longest prison term on record for a South Korean conglomerate executive if the court finds him guilty when it makes a ruling Aug. 25, two days before Lee's current period of detention ends.

Other charges he faces include wrongfully transferring assets overseas and hiding the proceeds of a crime.

"I have never asked anyone, including the president, for anything for the company or my personal gain," said Lee in a final statement, his voice wavering. He stopped several times during his speech, holding back tears.

"I deeply regret that I have given such disappointment and apologise," he said.

Samsung Electronics offered no comment regarding the prosecutors' demand. The company's shares ended down 0.3 percent on Monday, erasing minimal gains seen early in the session.