The memo calls for a full independent inquiry focusing on how the White House used information to justify an attack on Iraq. 

Many Democrats believe that the inquiry should be held next year, which would coincide with presidential elections.

The memo, which was shown on an American television new channel read: ''We can pull the trigger on an independent investigation of the administration's use of intelligence at any time. The best time to do so would probably be next year.''

Some Democrats running for the presidency have accused the White House of exaggerating the threat posed by Iraq's weapons of mass destruction programme to launch an invasion of the country.

Republicans are keen for the inquiry to focus on the accuracy of the intelligence gathering leading up to the invasion of Iraq, while Democrats want the inquiry to be far broader focusing on the use of information.

Troubling
 
Senate intelligence committee chairman Pat Roberts, a Republican, says he found the memo ''very troubling'', adding ''I'm pretty despondent right now, it's sort of like a personal slap in the face after you have worked over time to come up with what we think is going to be a very good report on how to improve our intelligence capabilities,'' he said.

The White House, along with the CIA, Pentagon and State Department, has been asked to submit documents to the committee.

The Bush administration has said it will co-operate with the inquiry, but some committee members claim that as yet no documents have been made available to the inquiry.

The committee is expected to produce a draft report by the end of the year.