In an interview to Strana.ua, Onishchenko said that in 2014, Poroshenko asked him to find a lawyer in order to return his company Neftegazdobycha, which is the largest private operator of hydrocarbon fishing in Ukraine. Former MP says that a few years ago, Poroshenko lost share in the company, which was owned by Nestor Shufrych and Mykola Rudkovsky. They "found fantastic deposits" and sold the company to businessman Rinat Akhmetov.

Onishchenko says that as president, Poroshenko asked the Minister of Ecology and Natural Resources of Ukraine Igor Shevchenko "to create licence problems for Neftegazdobycha" and force Akhmetov to negotiations in the proper manner.

According to the former deputy, depriving Akhmetov of mining licenses failed, as Prime Minister Arseniy Yatsenyuk, who "built a strong communication with the billionaire", was against it. Allegedly, this is what led to the conflict between Poroshenko and Yatsenyuk.
Onishchenko says that Poroshenko personally demanded Akhmetov pay him $200 million, but he refused.

Shevchenko told the newspaper that he had been asked to "contribute as much as possible to return the stolen deposits", explaining that Neftegazdobycha was associated with exile Edward Stavisky, who in the days of Victor Yanukovych held the post of Minister of Energy and Mines.

Akhmetov's DTEK confirmed the attacks on Neftegazdobycha through the Attorney General's Office of Ukraine, without confirming Poroshenko's involvement.

On December 24, Time magazine published an article written by Onishchenko, in which he accused Poroshenko in the multimillion-dollar kickbacks from every contract involving state-owned enterprise in Ukraine. Former member of Parliament in his article also accused the country's president that he spent most of the funds received from the IMF to the war.

Former deputy Onischenko is suspected in Ukraine of embezzling funds through the creation of "a gas scheme". According to the National Anti-Corruption Bureau of Ukraine (NABU), Onishchenko's actions inflicted damage to the state in the amount of 3 billion USD. On July 5 Verkhovna Rada withdrew Onishchenko's immunity, and gave permission for his arrest.