Ken Clarke has blamed pressure from President Obama for last week's humiliating Commons defeat preventing David Cameron from launching military strikes on Syria.
Last Thursday the prime minister recalled parliament at short notice in order to gain MPs approval for the British military to take part in US-led attacks on the regime of Bashar al-Assad.
The fact MPs were brought back to Westminster just four days before they were originally scheduled to return raised suspicions it had been done as strikes were due over the following 72-hours.
Clarke told Channel 4 News yesterday: "The Americans wanted us to make this vote very quickly."
"But people were so scarred by the experience of Iraq we did not manage to get across to enough of our people that we were not repeating the gross error of Iraq, and then Ed Miliband pulled most of the Labour Party out."
The cabinet minister, who himself missed the vote due to family reasons, added: "We did not get a majority because of the trauma of the Iraq War."
In the event Cameron lost the vote and president Obama subsequently decided to ask the US congress to approve his plan to strike regime targets rather than launching an immediate attack.
Tensions over Syria are expected to dominate a summit of the world's major economies being held in Russia in the run-up to an expected US military assault which host Vladimir Putin has warned would be an act of aggression.
Cameron risks being sidelined at the G20 gathering in St Petersburg, after ruling out British involvement in any military action in the wake of his shock Commons defeat.
He is not expected to have a formal bilateral meeting with Obama, who is leading the international drive for an armed response to Assad's apparent breach of the prohibition on the use of chemical weapons.
Obama last night cleared the first hurdle to obtaining Congressional approval for a strike, as the influential Senate Foreign Affairs Committee backed the use of force by a margin of 10-7, moving the measure to a full Senate vote next week. The proposal allows the use of force for 60 days, with the possibility of a 30-day extension.
The president has said he is confident of receiving approval from Congress for "limited and proportionate" military action, which he said would not involve US troops putting "boots on the ground" in Syria.
Assad had flouted a chemical weapons ban enshrined in treaties signed by governments representing 98% of the world's population, he said, adding: "I didn't set a red line. The world set a red line."