Ukrainian lawmakers said on Monday parliament should investigate allegations that President Petro Poroshenko used an offshore firm to avoid tax, following a global leak of documents from a Panama-based law firm over the weekend.
Leshchenko and a fellow reformist lawmaker - Mustafa Nayyem - said Ukraine's parliament, the Rada, should launch a special investigation into the allegations.
"The only way out of this situation is with complete openness and transparency at all stages of the unravelling of this scandal," Nayyem said on Facebook.
According to the International Consortium of Investigative Journalists, Poroshenko set up an offshore company to move his confectionery business, Roshen, to the British Virgin Islands in August 2014 during a peak in fighting between Ukraine and rebels.
Poroshenko has not commented publicly. His office said a law firm representing companies named in the leaks would make a statement later on Monday. A senior official in the General Prosecutor's office said the leaked documents did not show Poroshenko committing any crime.
The ICIJ on its website published a response from an unnamed spokesman of Poroshenko. The spokesman said the company, Prime Asset Partners Limited, of which Poroshenko became the sole shareholder, was part of a corporate restructuring to help sell the Roshen group in line with prevailing market practices.
Poroshenko, who came to power after protests in 2014, has already faced criticism over Roshen for not selling it despite promising to do so. Last year Poroshenko had said unfavourable market conditions made selling Roshen difficult.