"It is important to prove that these actions are legally wrong. And that's why we will start legal proceedings tomorrow [on Monday]," Kachka told a newspaper on Sunday.
He added that "all the world" should see how the EU member states treat their trade partners and the bloc itself.
"The systemic approach of Budapest and Warsaw of ignoring the position of the EU institutions in trade policy, I think that will be a problem for the EU in general, because there is no unity there," Kachka explained in an interview.
The official called the bans "ridiculous," adding that they would probably affect a significant part of Ukraine's exports, forcing Kiev to introduce retaliatory sanctions and prohibit the import of fruits and vegetables from Poland.
Later on Monday, WTO told Sputnik that it had not received any request from Ukraine to initiate dispute proceedings over the ban of the country's grain imports.
Earlier, Polish Agriculture Minister Robert Telus said that Poland would not let Ukraine into the EU unless the issue of grain exports is resolved.
"If we do not create these tools today, Poland will definitely not agree to Ukraine's accession (to the European Union). We need to create tools today, because we will live longer with Ukrainian products. When Poland joined the EU, we had to meet the conditions. And these conditions were very hard. And we have to set conditions for Ukraine," Telus said.
On September 15, the European Commission announced it would lift a ban on duty-free Ukrainian grain imports to five neighboring countries of the European Union, as well as a demand that Kiev introduce export controls. Following the decision, Poland, Hungary and Slovakia announced the unilateral extension of the ban.