Ross had submitted his evidence to the Butler inquiry, the committee set up to investigate the accuracy of British intelligence into Iraq's weapons of mass destruction.
He said: "With the exception of some unaccounted-for Scud missiles, there was no intelligence evidence of significant holdings of CW [chemical weapons], BW [biological weapons] or nuclear material."
Ross also said that when the US suggested "regime change" he and other diplomats argues against such a move, "primarily on the grounds that Iraq would collapse into chaos".
The prime minister's office did not comment.
"There was no intelligence evidence of significant holdings of chemical weapons, biological weapons or nuclear material"
former British diplomat
The Independent, a UK daily newspaper, reported that the Select Committee on Foreign Affairs, a body of lawmakers in the lower house of Parliament, published the evidence after seeking assurances from the Foreign Office.
Previously the comments had been kept secret as Ross feared he might face prosecution under the Official Secrets Act.
Ross's evidence challenges the assertions of Tony Blair, the British prime minister, that war with Iraq was legally justified because Saddam possessed weapons of mass destruction that could be deployed within 45 minutes.
The Butler inquiry was established in 2004 to "examine any discrepancies between the intelligence gathered, evaluated and used by the Government before the conflict, and between that intelligence and what has been discovered by the Iraq Survey Group since the end of the conflict".
The inquiry absolved Blair of distorting intelligence but contradicted claims that Iraq's weapons were ready for use and showed that vital caveats were dropped from the spies' assessments.
Ross also suggested Britain failed to crack down on Iraq when the country was in breach of UN sanctions due to "inertia" and "inattention" on the part of government ministers.
Ross was responsible for handling Britain's Iraq policy at the UN from 1998 to 2002 and resigned from the Foreign Office in 2004.