The archbishop started the relationship with the 20-year-old woman when she was as young as 14 years old, news that is certainly going to shake the Catholic faithful in Nigeria.
This is because sex scandals, child molestation and inappropriate relationships involving priests are not too common in the country.
Archbishop Richard Anthony Burke, 61, was investigated by the Catholic Church in Benin, which passed on its findings to Saint Patrick Missionary Society in Ireland, to which he belongs.
Investigations show he had the relationship with the lady.
The Archbishop has apologised in a Catholic newspaper in Ireland, stating his "deepest sorrow for his inappropriate, irresponsible and repeatedly sinful conducts".
Burke served at various times in Warri in Delta state and Benin in Edo state in the Niger Delta area of Nigeria.
He was even involved in several negotiations between rebels and government officials when foreigners were kidnapped in the Niger Delta area. The Catholic Church in Nigeria is yet to comment publicly on this matter.