Two members of the United Progressive Party are not the only ones accused of being elected to the National Assembly in April by fraudulent means. Similar charges are being hurled against five lawmakers of the ruling Saenuri Party.

A text message service provider reportedly purchased the list of the ruling party’s 2.2 million members in March. It signed a contract on the provision of its text message service with 29 politicians seeking party nomination. Of the 10 of them that were nominated, five were elected to the National Assembly, according a report by Channel A, a cable TV channel, on Wednesday.

If the news report proves to be true, the conservative ruling party will have to take disciplinary action against the lawmakers. The main opposition Democratic United Party has already demanded that the five lawmakers resign voluntarily. Otherwise, it says it will bring the case to the ethics committee of the National Assembly.

Earlier in the week, the ruling party claimed that eight had been provided with the texting service from the company and that one of the two that had been nominated among them won the election. But the elected one, the party said, had been handpicked by the party for a nomination, instead of winning it through a primary, claiming that he had no reason to abandon his parliamentary seat.

As the criminal investigation into the case is widening, the main opposition party is putting pressure on the ruling party to withdraw party membership from the suspected lawmakers and force them to resign as members of the National Assembly. It has good reason: The ruling party made similar demands when the two lawmakers of the United Progressive Party were accused of vote-rigging for their nominations.

The scandal in the ruling party is also a setback for Rep. Park Geun-hye, the frontrunner among the party’s presidential hopefuls, given that her faction exercised dominant influence on the selection of nominees. Her critics are already on the offensive against her.

Now the prosecutors’ office is called on to conduct an unbiased investigation into the case involving the suspected Saenuri lawmakers. It needs to keep in mind that any suspicion about its investigation into the case will undoubtedly raise questions about its impartiality toward the progressive opposition party. It will be also accused of being obedient to powerful people.