Blair, in power at the time of the US-led invasion in 2003, gave evidence to the inquiry in January, saying he had no regrets about the war and that Saddam Hussein was a threat to the world who had to be removed or disarmed.

His comments angered relatives of the 179 British soldiers who were killed in Iraq.

“As we draft our report it is clear that there are some areas where we need further detail,” Chilcot said in a statement.

“We will, therefore, be seeking further evidence on those maters,” he added, listing Blair and former Foreign Secretary Jack Straw among 12 people who had been asked to give evidence.

They will appear between Jan. 18 and Feb. 4 in 2011.

Former International Development Secretary Clare Short disputed evidence Blair had given when she appeared before the five-person inquiry a few days after him.

Short, a long-time critic of Blair, said Blair had not wanted Iraq discussed in the cabinet because he feared leaks to the media. Blair had said there had been “substantive discussion” with senior ministers in cabinet.

The decision to go to war alongside the United States was the most controversial of Blair’s 10-year premiership, provoking huge protests, divisions within his Labour Party and accusations he had deceived the public about the reasons for the invasion.

Blair eventually stood down as prime minister in 2007 and was replaced by Gordon Brown, who lost the election in May of this year.

Feelings still run high over Iraq and Blair was forced to cancel a book-signing session in London in September because of planned protests by anti-war campaigners.

The Chilcot Inquiry is seeking to learn the lessons from the war and is not a court of law.

“We are independent of government and will not shy away from criticizing if we find fault or if we conclude that errors have been made,” Chilcot said.