It's estimated that the militant group makes at least £23m from the artefacts it is taking from churches as it takes control of large parts of the Middle East.
Former Deputy Director of Europol, Professor Dr Willy Bruggeman, told Premier the militants were causing 'irreparable damage' to Christianity in Iraq and Syria.
He said the sale of artefacts is 'booming' and that IS has no problem selling the pieces on.
It's 'part of a broader process of genocide or ethnic cleansing,' Prof Bruggeman said, explaining that the group didn't just want rid of the people but also any other trace of their religion.
"It's to kill the identity of the people they are fighting, those who do not agree with Islam, archaeological objects are part of their culture so they want to destroy these objects," he said.
He was speaking at a meeting of a cross party group of MPs who were trying to find a way to cut down on the trafficking of art work.
The All Party Parliamentary Group for International Freedom of Religion or Belief was highlighting the destruction of cultural heritage in Syria and Iraq.
Professor Bruggeman added that being able to sell the precious art was vital to Islamic State: "They have to buy weapons, they have to undertake organisation for the fighting units.
"So, that takes a lot of money."
Walk of Truth is an organisation trying to stop the trafficking of artefacts.
Founder Tasoula Hadjitofi told Premier Islamic State will keep stealing the pieces until the demand stops.
"We need to bring to justice people who deliberately destruct the cultural heritage of the other.
"We need to set up a code of conduct for the auction houses and we should look at our own moral compass and decide what we should and shouldn't buy."
She also called for people who had bought stolen art work to return it so it can be taken back to the Middle East when the fighting is over.
