Ukrainian presidential candidate Volodymyr Zelensky suggests holding a referendum before a decision is made on the issue of Ukraine's accession to NATO and the European Union so that no one can revise this decision in subsequent changes of administration in the country, Dmytro Razumkov, a political consultant and an adviser with Zelensky's headquarters, said.

"The position on European integration is reflected in the program and speeches of Volodymyr Zelensky. We are moving toward Europe. It's a choice Ukrainian society has made. The only thing our opponents are trying to get to is a referendum," he told Interfax-Ukraine on Monday, commenting on the position of President Petro Poroshenko's headquarters that the incumbent president should be supported by the pro-European candidates in the second round of the election.

Referendums need to be conducted before accession to NATO and the EU to prevent anyone from revising their outcomes in changes of the administration, Razumkov said, adding that "it was the president's idea, the parliament's vision, the idea of the prime minister, some separate minister or the entire Cabinet of Ministers," he said.

"It will be a decision of the people of Ukraine, which will be very, very difficult to contest. Unlike our opponents, we aren't doing it during the election campaign, we aren't trying to pull a PR stunt by making changes to the Constitution that don't take Ukraine even half a step closer to entering NATO and the EU," the adviser with Zelensky's headquarters said.

Razumkov also said pro-European approach is definitely not determined by the scandals that shook Ukrainian society in the past months or the abolition of the article on illegal enrichment five years after the start of the anti-corruption reforms.

He said he believes many steps taken by the incumbent president and the political elite are not supported by Ukraine's European partners and "play into the hands of Russian aggression."