He died Tuesday morning at the Greater Accra Regional Hospital, formerly Ridge hospital, Myjoyonline.com reports.
He died three days after marking his 76th birthday on March 9, 2019.
Dr. Adjei graduated with a PhD in Research Methods and Statistics in Psychology from the University of Strathclyde, Glasgow, Scotland, U.K in 1973.
He ventured into politics in 1978, getting elected as a Council Mmember of the Jasikan District Council in the Volta region.
The late Dr Adjei was the chairman of the NDC when the party won power in 2008. He had been battling with a protracted sickness.