Christian charity Open Doors has said that the existence of Christians is on the line within Iraq.
Before the war nearly 1.4m Christians were living in the country, mainly Catholic Chaldeans. However the number is estimated to be between 250,000 and 300,000.
Many are also now losing ownership to their homes.
Rt Rev Mar Shimun Daniel, Bishop of the Diocese of Iraq and the Middle East region told Premier the reasons for the decline.
He said: "It is very tragic and sad, because since 2003, Christians became a target for other radical groups, they have been killed, they have been kidnapped, and also they have been blackmailed.
"In addition to that, many of their properties and belongings have been taken forcibly and their towns and cities have been invaded by the by ISIS, and they've been displaced forcibly.
"So all of what happened to the Christians since 2003 until now has led to decreasing in their numbers."
"In 2014, when ISIS attacked Christian cities and villages, all of these places became empty of any Christian existence.
"Around 120,000, people left their houses in one day and then 2016, after the liberation of Mosul, 45 per cent of that number were able to go back to live in their homes and cities, because most of their churches and houses were fully destroyed by ISIS."
According to Bishop Mar, those affected have started to rebuild the infrastructure they lost, but there are still some homes require additional work.
Bishop Mar believes that Christians can have a big impact in changing the shape and the future of Iraq.
He said: "Because we're always asking for peace. We're always asking people to love each other and to forgive each other.
"So I think the existence of Christianity in Iraq is given a big example to the others, because we are, we're showing love to our neighbours we shown peace and we're always praying so that our country will live in peace and harmony."