The son of the European Council president was questioned Wednesday by a Polish parliamentary commission as a witness within an investigation into one of the country's biggest financial scams.

The questioning was seen by many as part of the current ruling party's effort to undermine their political foe, former prime minister Donald Tusk, in Poland and in the EU. Led by a member of the conservative ruling Law and Justice party, the commission has indicated it will want to question Tusk himself.

Donald Tusk's son, Michal Tusk, had worked as spokesman and consultant for the OLT Express airline, which was a subsidiary of Amber Gold para-bank, a business that turned out to be a pyramid scheme.

The scam was operated by a couple between 2009 and 2012, when Donald Tusk was prime minister. It deprived some 19,000 people — many of them elderly — of savings worth some 850 million zlotys ($219 million).

During the hours-long public hearing on Wednesday, the commission wanted to know how Michal Tusk got the job and what his role was in the airline. The panel asked about his acquaintance with the couple who operated Amber Gold and who are now under arrest and on trial over the scam.

Michal Tusk rejected speculation included in the commission's questions that his employment by the airline might have shielded the scheme from state control.

He said his father did not help him get the job and that he had no influence on the outcome of Amber Gold and OLT Express activities.

The commission's findings may lead prosecutors to open more investigations.

The commission says its aim is to find out why Donald Tusk's government, financial control institutions and prosecutors failed to stop the scheme or warn people.

Donald Tusk was questioned by prosecutors in Poland earlier this year in another case linked to the 2010 plane crash that killed President Lech Kaczynski, and has received summons to another questioning in July. He has indicated that if the summons interferes with his EU duties he might use his immunity as EU Council head.