Civilian deaths have caused friction between the US and President Karzai
The number of civilians killed in the conflict in Afghanistan rose 39% last year, the United Nations says.
Militants were to blame for 55% of the 2,118 civilian deaths, while US, Nato and Afghan forces were responsible for 39%, according to the UN report.
Civilian casualties have increased despite repeated pledges by US-led forces to reduce civilian deaths.
The data came as a US Congress-funded think tank said it was unlikely the US and Nato would defeat insurgents.
The Institute of Peace called for new forces deployed in the country to be used to train Afghan security forces.
The UN report into civilian deaths said the death toll in 2008 civilian was "the highest of any year" since the Taleban were ousted in 2001.
The majority of the victims were killed in the south of the country - where international and Afghan forces are fighting a fierce counter-insurgency campaign.
In one of the most-publicised incidents, US troops fighting off a Taleban ambush last November bombed a wedding party in the Shah Wali Kot area in southern Afghanistan, killing about 40 civilians - mainly women and children.
The issue of civilian deaths at the hands of foreign troops is a hugely sensitive issue, says the BBC's Martin Patience, in Kabul, and is something that the Afghan President, Hamid Karzai, has raised repeatedly.
Relations between Kabul and Washington appear to have soured even in the four weeks since US President Barack Obama took office, although the US envoy to the region, Richard Holbrooke, met Mr Karzai in Kabul over the weekend.
Despite the high number of civilian casualties inflicted by international forces, more than half of the casualties recorded were inflicted by the militants fighting the foreign troops.
The UN said insurgents had inflicted the overwhelming majority of deaths in bombings, 65% more than the year before, and they were often carried out "with apparent disregard for the extensive damage they cause to civilians".
In one of the worst cases, a suicide car bomb killed 14 primary schoolchildren in Khost province at the end of December in what officials said was a failed attempt to blow up a meeting of tribal elders.
The researchers estimate that two-thirds of the 828 Afghans killed by the pro-government forces died in air strikes targeting militants, sometimes at night.
Nato rejected the UN figures, saying its forces had caused 237 civilian deaths.
The large difference in the numbers was down to the different methodologies used to collect the data, according to Nato spokesman Major Martin O'Donnell.
Last week the Afghan leader announced that NATO-led forces had accepted new procedures proposed by his government - to try and reduce the number of civilian deaths.
The human rights team of the UN Assistance Mission in Afghanistan, which collected the figures for the report, said about 130 people had died in incidents such as crossfire. It was not able to say who had killed them.