The general who headed the British army during the Iraq invasion said in comments published Saturday that the current unrest there was caused by a US decision to deploy insufficient forces and to scrap diplomats' post-conflict plans. Retired Gen. Sir Mike Jackson said former US Defense Secretary Donald Rumsfeld's approach to the invasion was "intellectually bankrupt" and that his claim US forces "don't do nation-building" was nonsensical, according to quotes excerpted from his autobiography and published by The Daily Telegraph. Rumsfeld "refused to deploy enough troops to maintain law and order after the collapse of Saddam's regime, and discarded detailed plans for the post-conflict administration of Iraq that had been drawn up by the US State Department," the newspaper wrote, paraphrasing Jackson. "All the planning carried out by the State Department went to waste," Jackson wrote. For Rumsfeld and his neo-conservative supporters "it was an ideological article of faith that the coalition soldiers would be accepted as a liberating army." Jackson, who retired in August 2006 as chief of the general staff, described Rumsfeld as "one of those most responsible for the current situation in Iraq." In his book, which the newspaper will serialize starting Monday, Jackson criticizes the US approach toward tackling global terrorism as inadequate, accusing Washington of relying too heavily on military power at the expense of nation-building and diplomacy. Jackson's comments were the most outspoken criticism of US policy in Iraq yet by a senior British officer, but he was soon backed by other top ranking British military figures as well as by members of the opposition. Maj. Gen. Patrick Cordingley, who commanded British troops in the first Gulf War, told Sky News television Jackson's analysis was "absolutely spot on," while Maj. Gen. Tim Cross, deputy head of the coalition's Office of Reconstruction and Humanitarian Assistance in 2003, said Washington's postwar plan had been "fatally flawed". "Right from the very beginning we were all very concerned about the lack of detail that had gone into the postwar plan and there is no doubt that Rumsfeld was at the heart of that process," he said in comments published in the Sunday Mirror. "The US had already convinced themselves that following the invasion Iraq would emerge reasonably quickly as a stable democracy. Anybody who tried to tell them anything that challenged that idea - they simply shut it out." Conservative lawmaker Sir Malcolm Rifkind said he backed Jackson's comments, calling Rumsfeld incompetent and attacking US President George W. Bush for putting the military in charge of nation-building after the end of the war. Jackson has a reputation for outspokeness, reportedly refusing an order from US Gen. Wesley Clarke to confront Russian forces rushing to secure Kosovo's Pristina Airport in 1999. "I'm not going to start the Third World War for you," he was widely quoted as saying. More recently, Jackson warned that British troops faced fierce combat in Iraq and Afghanistan without adequate resources or government support. In an interview with the Telegraph on Saturday, Jackson defended British forces' performance in southern Iraq, dismissing charges made by a US general last month that Britain had allowed deteriorating security in southern Iraq to get worse. "I don't think that's a fair assessment at all," Jackson was quoted as saying.