Here is the Butler report:
http://image.guardian.co.uk/sys-files/Politics/documents/2004/07/14/butler.pdfStarting on page 122:
In early 1999, Iraqi officials visited a number of African countries, including Niger. The visit was detected by intelligence, and some details were subsequently confirmed by Iraq. The purpose of the visit was not immediately known. But uranium ore accounts for almost three-quarters of Nigera's exports. Putting this together with past Iraqi purchases of uranium ore from Niger, the limitations faced by the Iraq regime on access to indigenous uranium ore and other evidence of Iraq seeking to restart its nuclear programme, the JIC judged that Iraqi purchase of uranium ore
could have been the subject of discussions ...
During 2002, the UK received further intelligence from additional sources (which were?) which identified the purpose of the visit to Niger as having been to negotiate the purchase of uranium ore, though there was disagreement as to whether a sale had been agreed and uranium shipped.
(Wow. Sounds authoritative!)
*****
That's it. According to the text of the Butler Report, that's all the evidence for an Iraqi purchase for Niger uranium.
1) An Iraqi delegation reportedly went to Niger in 1999 causing some analysts to guess that the purpose of this trip was to obtain yellowcake based on Niger's exporting profile
and
2) Unnamed sources (can you say "exiles"?) "confirmed" this Iraqi interest in 2002, although these unnamed sources couldn't even agree if any uranium was actually purchased.
That's it. That's the sum total of the "credible evidence" that backed these "well founded" (but completely inaccurate) claims.
Meanwhile:
http://news.bbc.co.uk/2/hi/africa/3891503.stmNiger's former prime minister has said that Iraq did not try to buy uranium, contradicting claims made in the build-up to the invasion of Iraq. Ibrahim Mayaki told the BBC that no Iraqi delegation went to Niger while he was foreign minister or prime minister.
An official report into UK intelligence supported the claims that Iraq had sought to buy uranium from Niger. Although some documents backing up this claim were shown to be forgeries, the UK has not withdrawn the charge. Last week's US Senate report on the intelligence leading up to the Iraq invasion said that Saddam Hussein's government may have tried to buy uranium from Africa. Following the discovery of the forgeries, President George W Bush withdrew the charges.
Mr Mayaki denies allegations in the Senate report that he admitted meeting a delegation from Iraq in 1999.
...
"I think this could be easily verified by the Western intelligence services and by the authorities in Niger," he said. So even the very basis of these erroneous reports was a fabrication!