A former diplomat at the centre of events in the run-up to the Iraq war revealed yesterday that the government has a "paper trail" that could reveal new information about the legality of the invasion.

Carne Ross, who was a first secretary at the United Nations in New York for the Foreign Office until 2004, told MPs: "A lot of facts about the run-up to this war have yet to come to light which should come to light and which the public deserves to know." There were also assessments by the joint intelligence committee which had not been disclosed, Ross told the Commons public administration select committee.

He told the inquiry that the intelligence made it "very clear" that Saddam Hussein did not pose a significant threat to the UK, as was being claimed at the time by ministers, and that tougher enforcement of sanctions could have brought his regime down.

He said he tried to inform ministers about his misgivings over the developing momentum towards war, taking them aside during their visits to New York or having brief conversations in their car to the airport.

But he said he was aware that speaking out too often or too openly - even in internal debates - about his concerns about the government's policy direction would damage his career by winning him a reputation as a "naive troublemaker".

Ross's evidence, by video link from New York, came days after Jack Straw, who was foreign secretary at the time, used the first ministerial veto under the freedom of information act to ban the release of cabinet minutes on the decision to go to war.

"I feel very strongly that there has still not been proper accountability and scrutiny into what happened in Iraq," Ross said.

"There should be a full public inquiry or parliamentary inquiry into the decision-making that took place. Hutton and Butler are by no means sufficient to that purpose and it is disgraceful that the government pretends that they are... if we had those systems of accountability and scrutiny then leaking and other more aberration behaviour from civil servants would be less necessary."

He was one of four "whistleblowers" who yesterday gave evidence to the committee.

They also included Katharine Gun, a former GCHQ translator who revealed the organisation was tapping phones of countries that were against the Iraq war; Brian Jones, the most senior expert on chemical weapons at the Defence Intelligence Staff; and Derek Pasquill, a former Foreign Office official who leaked documents about rendition and Muslim groups who were hostile to the UK receiving government money.

Jones and Ross never leaked any information to the press. Jones instead complained to his superior that he thought the intelligence dossier on weapons of mass destruction was being exaggerated but was told that there was "one secret piece of information which could not be shared with [him]" because it was too sensitive.

He told MPs that when the WMD dossier was published and he saw the difference between the foreword by the prime minister and the contents he "thought the intelligence services were going to be crucified".

But he instead he found that most MPs, with a few exceptions, supported the government. "I feel that you gentlemen [the MPs] have been either deliberately or accidentally misled and these incidents have not been followed up. I think that there has been a great laxity and that won't encourage people like me or my colleagues to come to you," he said.

Tony Wright, the chairman of the committee, agreed with the allegation. "I think you are absolutely right to castigate parliament, which I think has behaved abysmally in this matter - endless bleating about the need for an inquiry but a complete failure to insist upon one," he said.

Gordon Brown has promised to look at an inquiry after all the troops come home from Iraq.