The Seoul Central District Court also ordered Lee Sang-Deuk, 77, to pay fines totalling 750 million won ($701,600) -- the same sum he was found guilty of taking in kickbacks from bankers and a businessman.

Lee, a six-term lawmaker, was arrested in July last year on graft charges and allegedly helping troubled banks avoid audits.

His activities were linked to a major corruption scandal in early 2011 when four savings banks were suspended for inadequate liquidity, triggering a wider probe.

So far 16 savings banks have been suspended and four bankers have committed suicide.

Lee was the main contributor to his brother's election victory in 2007, but critics said he tried to wield too much influence over state affairs.

The verdict is an embarrassment for the president who has already had to apologise for a series of corruption cases involving close aides.