Story highlights Investigation underway into who ordered Iraqi troops to withdraw from Ramadi, letting ISIS take the city last month

Iraq's prime minister was not aware the order was given, raising big questions, parliamentary speaker says

The question of why Iraqi troops left the city has sparked an international blame game

Baghdad, Iraq (CNN) Iraqi troops left the strategically vital city of Ramadi -- allowing it to fall to ISIS -- because of a direct order from their military commanders of which Iraqi Prime Minister Haider al-Abadi was not aware, according to the powerful Sunni speaker of Iraq's parliament.

Salim al-Jabouri, arguably the most powerful Sunni politician in the country, told CNN that Ramadi was abandoned last month because of "a clear decision to give the order to pull out -- and after that Ramadi fell."

Al-Jabouri added: "Even the Prime Minister -- the general commander of the armed forces -- was not aware of the orders to pull out. This led to big questions for us. Who has a direct interest in the army pulling out and not confronting ISIS?"

Asked who gave that order, he replied: "In command was the Golden Division, and after they withdrew, a collapse occurred, and ISIS controlled Ramadi." He said it was unclear where the order to withdraw originated -- whether the Golden Division was ordered to pull out by a higher command, or did so on its own. A parliamentary investigation is under way to establish these facts, he added.

"There are a number of answers that we need to confirm in a realistic form," he said. "We fear that there are other hands involved in this that played a role in military decisions."