WARSAW, Poland (AP) — Top European Union official Donald Tusk is being questioned by a panel in his native Poland that is investigating cases of large-scale tax evasion during the time when he was the country's prime minister.

Tusk's questioning is seen as an attempt by the ruling party to discredit him and his political circle, who are its main political foes. The right-wing Law and Justice party wants to strengthen its position before fall parliamentary elections.

A panel of lawmakers was asking Tusk Monday why his government in 2007-2014 failed to curb illegal practices by private businesses relating to VAT, causing great losses to the state budget.

Another commission previously questioned Tusk about a 2010 plane crash that killed President Lech Kaczynski, the twin of powerful Law and Justice leader Jaroslaw Kaczynski.