Lars Rise also condemned the complete lack of democracy or the rule of law in Iraq more than ten years after the invasion by US and allied forces.
Mr Rise told a conference held by the British Parliamentary Committee for Iran Freedom: “We are completely shocked by the horrible events which took place in the early morning of 1st September.
“What made the most impression on me was to see the picture from the medical centre, to see that they had first shot them and didn’t manage to kill and then they went into the medical treatment room and actually assassinated the people in the beds.
“It is a very serious crime against humanity and there is of course a very strong need for an impartial investigation.”
Mr Rise, who visited camp Ashraf in 2005, said: “Where is the rule of law in Iraq ? Where is the democracy ?
“When we look at Iraq ten years after the speech of George Bush here in London… all the Western Foreign Ministries seem to be completely impotent or incapable of executing any kind of power.
“They just say to the Iraqi government, please will you investigate this ? This is so shocking, to see how they can go to a suspect and ask them to investigate.
“We now have hard evidence, we have technical evidence that the Iraqi government was behind this together with the Iranian government and UNAMI is also suspect, so neither UNAMI nor the Iraqi government should be part of any investigation.
“And we especially think of the seven hostages and how they can be saved. We all have a responsibility to do our utmost to secure their safety and their lives.”