Labor's defence spokesman, Stephen Conroy, has raised with the Chief of the Defence Force claims that senior US military officers manipulated reports on the war against Islamic State.

The New York Times is reporting that US intelligence analysts have accused their superiors of changing conclusions on the readiness of Iraqi security forces and the success of the bombing campaign in Syria.

The changes reportedly painted a better picture to the White House about how the war against IS was going.

The Daily Beast said the claims were supported by more than 50 intelligence analysts.

Senator Conroy told Lateline they were serious allegations.

"We've all lived through the invasion based on false intelligence information. No-one wants to see a repeat of that," he said.

The allegations — made public just before Australian fighter jets launched their first strikes on IS in Syria — are now being investigated by the Pentagon's inspector general.

"The investigation will address whether there was any falsification, distortion, delay, suppression or improper modification of intelligence information," a spokeswoman for the inspector general said.

Australian special forces soldiers are involved in training Iraqi forces, but the number of Australian soldiers in that role is being reduced from about 200 to about 80.

Senator Conroy said it would be "very concerning" if the intelligence Australia was receiving from the US had been tampered with.

He said he had raised the claims with the Chief of the Defence Force, as well as US officials.

"When you see 50 analysts potentially put their name to some fairly serious allegations, I think it deserves a full and independent investigation," Senator Conroy said.

"I think the fact that [US defence secretary] Ash Carter has put out a very specific instruction that says we don't want anything other than the unvarnished truth, [that] suggests that we've got to make sure that no-one thinks gilding the lily or misrepresenting or anything more serious is acceptable in a circumstance like this."

Conroy satisfied by response of Defence Force Chief

Senator Conroy said he was satisfied by the response of Defence Chief Air Chief Marshal Mark Binskin, who was confident in the intelligence being received.

But he said a thorough investigation into the issue was vital.

"I think everyone should be awaiting the report of the inspector general and he's an independent agency, so I think it's vital that a thorough investigation is held into this," the senator said.

"I think it would be a very serious situation if people had been doing any of the things described."

Meanwhile, Senator Conroy also poured doubt on allegations Australia had potentially caused civilian casualties in Iraq.

Earlier this month a US Central Command report listed an alleged incident where an Australian air strike against IS in Iraq may have caused civilian casualties.

Senator Conroy said he had been briefed on the issue.

"I don't believe that there's been any accusation that we have definitely killed civilians, but from the information — and I've received a full briefing on this — we have a system that works better than anyone else's in the world to minimise."

Number of civilians killed in dispute

The US-led coalition's bombing campaign in Syria is conducted under strict rules of engagement to avoid civilian deaths. But in spite of that, there is evidence emerging that many civilians are being killed.

According to Airwars, a not-for-profit group tracking the aerial war against IS, there have been more than 2,500 air strikes in Syria by US coalition forces since September last year.

With so many attacks, some civilian deaths are considered inevitable, but the numbers killed by coalition air strikes are in dispute.

This article contains content that is not yet available here.

The Pentagon maintains there have only been two civilian deaths from air strikes, but using multiple sources, the Airwars group claims that between 329 and 404 civilians have been killed.

"We use publicly available reporting of all these incidents and the reports can vary. Some may say 10, some may say 15, and so we have the minimum number and we have a maximum number," Airwars spokeswoman Kinda Haddad told Lateline.

"It's very difficult to verify these figures exactly, but these figures, they're 330 to 400 of the incidents that we consider to be very credible.

"So there's more than two sources. There's video footage, there's named civilians, and then there are other incidents which are more poorly reported and the figure then, if you include those, would jump to 500.

"But we are just taking into considerations the ones that are very well sourced and well reported."