During the past authoritarian governments, state prosecution was often exploited as a tool for suppressing the president’s opponents and critics. Businesses also fell victim to investigation by prosecutors acting under the command of the president.

The prosecution is not entirely free from this shameful legacy. It is still widely believed that prosecutors engage in investigations with political motives.

The prosecution’s months-long investigation of POSCO Group could be a good case in point. When it launched the corruption probe into the steel maker’s construction unit -- POSCO E&C -- in March, many thought it was intended to snare its former CEO Chung Joon-yang.

Why? Chung had a close relationship with people close to former President Lee Myung-bak, including his elder brother and former vice speaker of the National Assembly, Lee Sang-deuk.

President Park Geun-hye’s critics said she is following the habit of previous presidents by “predecessor-bashing” and that her administration targeted Chung. Park has not been on good terms with her predecessor, especially since she lost the 2007 presidential nomination race to him.

This assumption was fortified by the fact that prosecutors launched the probe by raiding the offices of POSCO E&C just one day after Prime Minister Lee Wan-koo declared a war against corruption, including alleged irregularities involving overseas resources development projects undertaken during the Lee administration.

At any rate, the investigation has plagued the operations of POSCO Group for the past five months, with its offices raided by investigators and about 100 executives and staffers being lined up for interrogation.

But what the prosecutors have done till now is the indictment of only a dozen people -- mostly incumbent and former executives of POSCO E&C and its contractors -- on graft charges. They came nowhere near the former CEO.

Prosecutors in the POSCO case came under fresh criticism last week when they were denied an arrest warrant for former POSCO E&C vice chairman Chung Dong-hwa. It was the second time -- the first being two months ago -- that the court turned down the prosecution’s request to detain Chung, citing lack of evidence.

Prosecutors said the former vice chairman is suspected of, among other things, running a slush fund, which they believed would lead to the former CEO Chung. But the court does not believe evidence on the former vice chairman is solid enough to take him into custody.

It is a disastrous result for the prosecution. Perhaps there was little to dig into in the first place, but the Park administration and prosecutors might have needed a big target in their ambitious anticorruption war.

As the probe into POSCO drags on, criticism is mounting over the prosecution’s exhaustive investigation. One such criticism came from Kim In-ho, a former economic technocrat who now heads the influential Korea International Trade Association.

Kim said at a forum last week that authorities should investigate businesses and businesspeople only when there are sufficient grounds and that they should take care to minimize the impact on business operations and activities. He also said that the change of government should not affect business activities and corporate personnel decisions.

Kim did not mention POSCO, but one can easily assume the steelmaker reeling from the extended probe and other cases of politically-motivated corruption investigations was on his mind.

Kim, a longtime technocrat who served such key posts as the fair trade chief and the top Blue House economic aide in the 1990s, would have had knowledge about the political relationship between the president and the prosecution. What he said last week shows that not much has changed.