Tony Blair's special envoy to Iraq on human rights has called on US-led forces in the country to protect suspected mass-grave sites.
Ann Clwyd has been 'moved' by what she has seen in Iraq
Ann Clwyd, who has been visiting Iraq, wants evidence collected at the sites to be preserved for possible use in future war crimes trials.
The Labour MP for Cynon Valley, in south Wales, made the comments on a visit to one of the largest mass graves so far uncovered in Iraq.
Speaking at the site, outside the central Iraqi city of Hilla, she told the BBC: "It's important that the evidence is preserved."
Ms Clwyd said the sites needed to be protected from ordinary Iraqis, who could destroy evidence while searching for missing family members.
"It's understandable that people want to come and find out whether the bodies of their relatives are here, but they also should be told that, at the same time, they might be destroying evidence," she said.
The MP travelled to the site with forensic experts from Britain who, along with other specialists, are teaching Iraqis how to preserve evidence, she said.
Ms Clwyd rejected criticism that not enough is being done by US and British forces to protect suspected mass graves in Iraq. There are at least 60 sites.
There are at least 60 suspected mass-grave sites in Iraq
"It's only seven weeks since the end of the war. The coalition are making every effort to make sure [preserving sites is] being done in a proper way," she said.
"What is being put in place now is a system that will ensure the evidence contained within them may be used some time in future at a war crimes trial against some of the people who perpetrated these terrible atrocities."
Ms Clwyd also told the BBC how she had been moved by what she had seen at the mass grave near Hilla, where up to 15,000 people are believed to have been buried.
"We could see the remains of people, a vertebrae, a finger, buttons, a comb, pieces of material - all those things that people use in their everyday lives."
The MP has campaigned for human rights in Iraq for 25 years and was one of the few left-wing Labour MPs who supported the military action in the country.
While in Iraq, she has also met women's groups.