Poroshenko's proposal comes as he trails in opinion polls on Ukraine's March 31 presidential election.
Poroshenko is running for a second term, but his record on fighting corruption is a topic of debate — with opposition lawmakers calling for his impeachment over graft allegations involving a close ally.
Ukraine in 2015 passed a law criminalizing illicit enrichment in 2015 as a condition of receiving bailout loans from the International Monetary Fund and for the European Union to grant visa-free travel to Ukrainian citizens.
But the Constitutional Court on February 27 overturned the law on grounds that it contravened the presumption of innocence.
"This morning I have signed, and now I am commissioning to register, a presidential bill which takes into account the remarks but preserves the key position — the inevitability of criminal punishment for illicit enrichment," Poroshenko said on February 28.
The Constitutional Court's decision was denounced by a Ukrainian law enforcement agency as a "step back" in the fight against corruption.
The National Anticorruption Bureau of Ukraine (NABU) said in a statement that the Constitutional Court’s ruling was "politically motivated and contradicts Ukraine's obligations on the ratified UN Convention against Corruption [and] its agreements with the International Monetary Fund and the European Union."
The agency said that about 65 corruption cases it is currently investigating and involving some $20 million will now be closed.
The court's ruling came two days after an investigative group in Ukraine made public the results of its investigation alleging that individuals close to President Petro Poroshenko's associates illegally enriched themselves by smuggling spare parts of military equipment from Russia.
One of the major presidential candidates, former Prime Minister Yulia Tymoshenko, announced on February 26 that her Batkivshchyna party and other political parties had started a process for Poroshenko's impeachment.
Poroshenko said on February 27 that he will instruct his government to draft new legislation to punish corrupt officials and that the text will be submitted to parliament as soon as possible.
Western officials say corruption hurts Ukraine's chances of throwing off the influence of Russia, which seized the Crimean Peninsula in 2014 and backs separatists whose war with Kyiv has killed about 13,000 people in eastern Ukraine.