Prosecutors launched an internal probe into allegations that the main opposition Democratic United Party’s senior advisor Rep. Sohn Hak-kyu bribed regional party members before last year’s Seoul mayoral by-election, officials said Tuesday.

A former party member recently claimed that Sohn, who was chairman of the then-Democratic Party at the time, summoned regional committee chairpersons to party headquarters in October and handed out envelopes, each containing 1 million won ($880) in cash.

The money was delivered as a bribe so the recipients would support left-wing candidate Park Won-soon in the mayoral race, he said.

The case was first referred to Seoul’s election commission but the panel delivered it to the prosecution as the six-month statute of limitations on election law violations is to expire next month, officials said.

The former DP chairman and potential presidential candidate denied all charges, accusing the informer of engineering a feud before the elections.

“Apart from party members, dozens of journalists were present on the scene and would have noticed if Rep. Sohn did anything out of the ordinary,” said Sohn’s aide.

“Legal actions are being considered, if necessary.”

The informer was stripped of his party membership late last year amid internal feuds over the party’s integration with the civic group-based Citizen Integration Party, the aide also said.

“The man repeatedly protested against the party’s direction and we suspect that he meant to cause a disturbance before the upcoming elections.”

Sohn won his fourth parliamentary term in last year’s by-election in Bundang-B but has refrained from seeking candidacy in next month’s race, pledging to support the party and its candidates.

By Bae Hyun-jung (tellme@heraldcorp.com)