The document, referred to as the Downing Street memo, apparently summarises a top-secret meeting between British Prime Minister Tony Blair and British intelligence officials in July 2002.
The document reportedly states the White House believed a war in Iraq was inevitable eight months prior to the March 2003 invasion, and that intelligence about weapons of mass destruction would be used to justify the removal of Saddam Hussein.
According to the memo, Mr Bush “wanted to remove Saddam through military action” and “intelligence and facts were being fixed around the policy.”
Both Mr Blair and Mr Bush have flatly denied any intelligence was construed to justify the Iraq war.
In a public forum at the Capitol, Democratic representative John Conyers was joined by other Democratic members of the House Judiciary Committee in demanding President Bush answer questions raised by the memo.
Mr Conyers said a list of questions will be delivered to the White House shortly, along with a letter signed by more than 100 members of Congress and half a million Americans.
White House spokesman Scott McClelland dismissed concerns about the memo as “rehashing old debates” and indicated there would be no response to the letter from the government.
Meanwhile, pressure is growing for a timetable on the US military withdrawal from Iraq, as Iraqi insurgent attacks swell and US public opinion turns against American involvement.
Republicans Walter Jones and Ron Paul joined Democratic representatives Neil Abercrombie and Dennis Kucinich in drafting a bill that would require Washington to announce by the end of the year a plan to start pulling-out US troops from October 2006.
But Mr McClelland immediately dismissed the proposal, saying it would send the wrong message to militants.
US State Secretary Condoleezza Rice has expressed concern over the dwindling popular support for America’s military presence in Iraq.
“I’m going to, like I think all members of the administration, perhaps try to do more to get out to the public to talk about what it is that we are trying to achieve and what it is we are achieving,” Ms Rice said.
A poll published this week by USA Today found that 59 percent of respondents want a full or partial troop withdrawal.