The trial of South Korean President Kim Dae-jung's second son for corruption has begun in a Seoul court, as a political row deepened between the country's ruling camp and opposition.

Kim Hong-up, 53, is charged with bribe-taking and evading taxes.

President Kim is feeling the heat

It is just the latest stage in a family scandal which has severely dented the reputation of President Kim. His youngest son, Kim Hong-gul, is already on trial on similar charges.

The heat on President Kim intensified further on Friday as the opposition Grand National Party threatened to impeach him over claims that the ruling party is waging a dirty war against the GNP's candidate for December's presidential elections.

The row comes ahead of important by-elections set for 8 August.

The ruling MDP, which President Kim founded, already faces becoming further weakened in the national assembly if the opposition - as expected - takes 10 seats, enough to give it an absolute majority.

The assembly gave President Kim a knock this week when it vetoed his choice of prime minister - Chang Sang - who would have been the country's first female leader.

Sons in trouble

Kim Hong-Up, who denies the allegations of bribe-taking and evading taxes, was arrested on 21 June. He is in jail in Seoul with his younger brother.

Hong-up, who appeared in court wearing handcuffs, said businessmen had asked him for favors. But he denied receiving any of the bribes his aides allegedly collected from businessmen on his behalf.

President Kim himself is not implicated in any of the scandals and he is in any case obliged to step down as leader at the end of this year.

Kim's troublesome sons: The charges

Kim Hong-up, 53 Taking $2.2m in bribes for influence peddling Taking $1.8m in "donations" from businesses and laundering the money to evade $497,000 in taxes Kim Hong-gul, 38 Accepting $2.9m from companies expecting favours Evading tax on $185,000 which he received from a lobbyist

But the allegations surrounding Mr Kim's family and aides has caused the popularity of the ruling Millennium Democratic Party (MDP) to plummet ahead of the upcoming presidential elections.

The GNP has demanded the MDP stop its "political scheming" ahead of the poll, and has called on the ruling party to apologise, according to the Yonhap news agency.

"Unless our demands are met, we may push for presidential impeachment and ouster of this regime," said Kang Jae-sup, head of a GNP committee formed to probe what it terms "political manoeuvring", Yonhap reported.

Alleged draft dodging

The MDP alleges that the GNP's presidential candidate, Lee Hoi-chang, has dodged mandatory military service.

The ruling party has also questioned Mr Lee's campaign fundraising in 1997, his alleged acquisition of a US$200,000 political fund from jailed venture businessman Choi Kyu-sun and e-mail exchanges between Choi and Mr Lee's son, Jeong-yeon.

The Seoul District Public Prosecutor's Office said on Thursday that it will launch an inquiry into the claim that Mr Lee avoided conscription - one of the issues which was said to be behind him losing the 1997 presidential race to Kim Dae-jung.

But recent opinion polls put Mr Lee about 10% ahead of MDP candidate Roh Moo-hyun, who was originally leading this year's race.