The 1993 death of then-Turkish president Turgut Ozal was "suspicious" and should be probed, according to a report by the country's presidential palace.
The report by the State Auditing Board, which is under the direct supervision of president Abdullah Gul, said there has been no satisfactory investigation into allegations by some family members and politicians that Mr Ozal might have been poisoned.
The report suggested forensic tests and an examination of hair samples to shed light on the allegations.
Doctors at the time said Mr Ozal, who underwent triple bypass surgery in 1987, died of heart failure.
Mr Ozal, who is of Kurdish origin, had pursued a moderate policy in an attempt to end a war by Kurdish rebels for autonomy in the country's south-east.
He had also pushed pro-Western policies following his election in 1989.