The following correction was printed in the Guardian's Corrections and clarifications column, Tuesday July 1 2008.

The article below was wrong to say that a household survey by the World Health Organisation and the Iraqi health ministry found that the rate of violent deaths had doubled in Iraq after the invasion. The survey did not make this finding. Figures that were unadjusted for under-reporting showed a doubling of the rate of all deaths and a violence-related death rate about 11 times higher. The article said the survey estimated that 151,000 civilians had been killed since the invasion. That figure included combatants.

An estimated 151,000 Iraqi civilians have been killed in the violence that has engulfed the country from the time of the US-led invasion until June 2006, according to the latest and largest study of deaths officially accepted by the Iraqi government.

The figures come from a household survey carried out by the World Health Organisation and the Iraqi health ministry. They are substantially lower than the 601,027 death toll reported by US researchers in 2006 in the Lancet using similar study methods, but higher than the Iraq Body Count's (IBC) register - based on press reports - of 47,668.

The authors of the WHO/Iraqi study, published last night in the New England Journal of Medicine, say that the new number, which could be anywhere between 104,000 and 223,000 allowing for misreporting, "points to a massive death toll in the wake of the 2003 invasion and represents only one of the many health and human consequences of an ongoing humanitarian crisis".

The Iraqi health minister, Dr Salih Mahdi Motlab Al-Hasanawi, said it was very important for the government to have reliable data on violent deaths. "There is controversy about reports from the media," he said. Some of the information that has been published "may be used or misused for political reasons and so on". The survey also collected data on the health of the population and availability of healthcare needed by the government.

The survey from the Iraqi Family Health Survey Group was carried out by trained employees of the health ministry who visited 10,860 households - 10 from each of more than 1,000 clusters across the 18 provinces of Iraq. Because of the insecurity, 115 (11%) of the clusters could not be visited - mostly in Anbar and Baghdad - so calculations were made to account for the probable number of deaths in those places. Researchers asked heads of households if there had been any deaths in the two years before or three years after the invasion in 2003.

Account was taken of under-reporting of deaths, which is usual in household surveys, not least because families often move when somebody dies. The survey also allowed for the out-migration of up to 2 million people between March 2003 and June 2006.

It found that 151,000 civilians died due to the conflict, which does not include accidents, suicides or deaths from disease. Unlike the Lancet study, it found no big increase in mortality across the three years. In 2003-4, 128 people died every day, in 2004-5 it dropped to 115 and in 2005-6 it rose again to 126. The daily death rates, according to the Lancet study, rose from 231 to 491 to 925.

Although the new figure is four times lower than the Lancet study, its authors, Gilbert Burnham and colleagues from Johns Hopkins University, believe their count of more than 600,000 is correct.

Les Roberts, one of the US authors who is now a professor in forced migration and health at Columbia University, said he was delighted to see the Iraqi government had accepted higher mortality figures. In June 2006 the government was relying on the IBC figure, which was 41,000. "For this to be coming from the Iraqi government is really healthy," he said.

It was also good for science that new studies were being carried out. "But I think there is overwhelming evidence that their estimate is too low."

The WHO/Iraqi study showed a doubling of the rate of violent deaths while the Lancet study showed a trebling. "Fundamentally, these studies are less different than people are thinking." But the US team's data was more accurate because all deaths were validated with death certificates. The health ministry admitted in the new paper that its figures before the invasion were too low, he said, which had also led to insufficient adjustment.