A former senior member of US intelligence today urged Parliament to hold an inquiry into what he alleges was a campaign of disinformation by British secret agencies in the run-up to war in Iraq.

Former UN weapons inspector Scott Ritter said he was involved with MI6 officers working on a secret operation codenamed Mass Appeal, designed to secure public support for action against Iraq by leaking dodgy intelligence to the media suggesting that Saddam Hussein continued to possess weapons of mass destruction.

And he said that disinformation was also supplied by a little-known body within the Defence Intelligence Staff called the Rockingham Cell, which provided intelligence officers to work as inspectors with the UN’s Unscom team.

Government scientist David Kelly told a closed hearing of the House of Commons Intelligence and Security Committee days before his death in July that he liaised with Rockingham when working for Unscom.

A former US marine and military intelligence officer who worked on the staff of General Norman Schwarzkopf in the Gulf War, Mr Ritter became a prominent opponent of war on Iraq after quitting Unscom in 1998.

He today said that ample intelligence was available to the UK and US governments before the war to show that Iraq’s WMD programmes were eliminated within a short period after the 1991 conflict, but that they chose to ignore this.

Operations like Mass Appeal – which has never before been publicly discussed – and Rockingham existed to support the case for continued sanctions on Iraq in the 1990s and war earlier this year, he argued.

Mr Ritter said he personally supplied Mass Appeal with information about WMD in the late 1990s which was not considered strong enough for Unscom to act upon, often because it came from a single, unreliable source.

As a senior inspector, he had access to “a body of data that was not actionable but was sufficiently sexy that if it could appear in the press would make Iraq look bad”, he said.

Mass Appeal took this information and “peddled it to the media, allowing inaccurate information to appear on the front pages of newspapers”, said Mr Ritter.

“The Government would feed off those reports to promote the notion that Iraq was a nation ruled by a dictator addicted to WMD.”

Meanwhile, Rockingham “cherry-picked” intelligence to construct the strongest possible case for the British Government’s policy of continued sanctions, and then war.

“Operation Rockingham was more than just an intelligence cell that massaged information,” said Mr Ritter. “It was an organisation designed to support a pre-ordained conclusion of the British Government that Iraq will never be found in compliance with UN Security Council resolutions.”

Its officers also fed dubious information back to Unscom in order to prompt inspection activity in Iraq, he alleged.

The activity turned up no proof of WMD, but gave the impression to the public that programmes were being concealed.

Speaking at Westminster today, Mr Ritter said: “I want to encourage the British Parliament to hold an investigation, with open hearings, into the role of British intelligence before the war.

“I leave it to the British Parliament to find who authorised this and how it happened. Are British soldiers serving in Iraq now because of a lie perpetrated by the British Government?”

He was backed by former minister Michael Meacher, who used an article in The Guardian to call for “a full-scale independent inquiry into the operation of the intelligence services around the top of their command and their interface with the political system”.

Mr Ritter declined to name his contacts in Mass Appeal and Rockingham or to identify individual pieces of misinformation which had been placed in the public domain.

He did not say whether he was referring to the notorious claims in last year’s Government dossier on Iraqi arms that Saddam had weapons ready to fire within 45 minutes and that Baghdad had sought to buy uranium from Niger for nuclear weapons.

But he said he was ready to set out all his information before a parliamentary inquiry, which he said should be able to subpoena members of MI6 to establish the truth.

Mr Ritter was backed by Ray McGovern, who was a senior CIA analyst until 1990, preparing the President’s daily intelligence brief and chairing the National Intelligence Estimates.

Mr McGovern said: “We have here what I would call a structural fault. You can’t have an intelligence service that is responsible both for objective analysis ... and that same intelligence outfit responsible for propaganda and Mass Appeal-type activities for rallying support and advocacy of a particular policy.

“I do believe that there is ample evidence that your Government cooked up this Mass Appeal evidence ... and deliberately deceived your populace and your Parliament into giving the go-ahead for an illegal and very ill-advised war.”

Similar problems had arisen in Washington with Defence Secretary Donald Rumsfeld’s creation within the Pentagon of an Office for Special Plans, which provided President George Bush with an alternative intelligence assessment on Iraq to that coming out of the CIA, he said.

Both men warned that yesterday’s terror attacks in Istanbul were a clear sign that the war had not prevented terrorism but fostered it.

“What happened in Turkey was a tragedy, but it was predictable and it could have been stopped,” said Mr Ritter.

“It could have been stopped in many ways, and the best way would have been not to have given the terrorists enhanced credibility by going to war in Iraq.”

Mr McGovern added: “Your Government and mine would not listen to the intelligence experts who warned that, far from a diminution of terrorism, an invasion of Iraq will increase terrorism to the Nth degree. That is what we saw yesterday in Turkey.”