South Korea's Constitutional Court has cleared the way for a special investigation into allegations of fraud against President-elect Lee Myung-bak.
President-elect Lee Myung-bak denies the allegations against him
The court dismissed a petition from Mr Lee's backers, which sought to halt the inquiry on the grounds that legislation authorising it was unconstitutional.
A special prosecutor will start working on the case next week.
Mr Lee won a landslide victory in last month's presidential election and is due to take office on 25 February.
Analysts believe the investigation is unlikely to be completed by then, and once Mr Lee takes office he will be immune from prosecution.
The 65-year-old former executive was dogged throughout his election campaign by allegations linking him to a financial scandal in 2001.
The case involved his alleged links to an investment firm at the centre of a share-rigging scandal.
In early December, prosecutors decided there was not enough evidence to charge Mr Lee.
But lawmakers then voted to re-open the case when a video emerged in which the president-elect was shown apparently saying he had established the scandal-hit company.
He denies the allegations and says his words have been taken out of context.
Mr Lee's supporters claimed that clauses in the law authorising a fresh investigation were unconstitutional.
But the court ruled that while one part of the law - enabling investigators to question witnesses without a warrant - violated the constitution, the probe could go ahead.