The National Environment Management Authority has said it will close county markets where traders are still using the banned plastic bags to package their products.
Nema on Friday noted that the use, manufacture and importation of single-use plastic bags was banned in 2017.
Since then, the authority has been enforcing the ban.
The authority said it will be taking enforcement action on market managers who condone the use of the banned bags and further close the markets.
"The authority has been working with county market managers, where they have been asked to ensure that no one uses the banned bags within their markets but rather use eco-friendly or biodegradable bags," Nema said.
However, the authority has noted with concern the continued use of illegal bags within various county markets and businesses licensed by counties.
Nema said it has already written to the Council of Governors led by Anne Waiguru to warn counties that enforcement action will be taken against the use of banned plastic bags.
"It's ironical that market managers cannot allow the sale of banned items such as bhang and other drugs, but are condoning the use of banned plastic bags," the authority said.
NEMA noted that the use of plastic bags is a crime as provided for under Section 145 of the Environmental Management and Coordination Act (EMCA), 1999.
Section 145 (1) of the Act says when an offence against the Act is committed by a body corporate, the body corporate and every director or officer of the body corporate who had knowledge of the commission of the offence and who did not exercise due diligence, efficiency and economy to ensure compliance with the Act, shall be guilty of an offence.
Section 145 (3) of the Act says a person shall be personally liable for an offence against the Act, whether committed by him on his own account or as an agent or servant of another person.