Didier Julia, an MP for French President Jacques Chirac's ruling party, said his efforts to release reporters Georges Malbrunot and Christian Chesnot failed after US troops opened fire on the convoy attempting to bring them out of Iraq en route to Syria.
Six of the French journalists' Iraqi escorts were killed in the US bombing barrage.
Julia's assistant, Philippe Brett, had persuaded the kidnappers to release the Frenchmen and they all left in two separate convoys from their place of detention, both of which had come under US fire, the MP said.
"They set up 20 roadblocks and six members of the team protecting the journalists were killed," said Julia, whose mission enjoys no backing from the French foreign ministry.
The ministry said it had no comment on the release effort or Julia's report of the US attack.
The MP said Brett learned of the mission's failure as soon as he arrived separately at the Syrian border and headed straight back to the journalists' captors.
The French foreign ministry is not
commenting on the accusations
"The three Frenchmen are still in Iraq in the hands of the resistance," he said.
"The Americans increased their bombardment and deployed two divisions to fire upon all terrorists who pass."
Julia, 70, is vice-president of the Iraqi-French Friendship Group. The two journalists have been held hostage by the Islamic Army of Iraq since August 20.
US rejects accusation
The US military on Friday rejected Julia's accusations that US troops had fired on a mercy mission to extricate the two kidnapped French newsmen, killing six escorts.
"I'd say that none of that is true. I have not seen any reports that would indicate any of these stories showing up are accurate or true," said senior spokesman Rear Admiral Greg Slavonic.