Decades of British and American intervention in the oil-rich Middle East motivated the London bombers, Ken Livingstone has suggested.
The London mayor told BBC News he had no sympathy with the bombers and he opposed all violence.
But he argued that the attacks would not have happened had Western powers left Arab nations free to decide their own affairs after World War I.
Instead, they had often supported unsavoury governments in the region.
Mr Livingstone was asked on BBC Radio 4's Today programme what he thought had motivated the bombers.
He replied: "I think you've just had 80 years of western intervention into predominantly Arab lands because of the western need for oil.
"We've propped up unsavoury governments, we've overthrown ones we didn't consider sympathetic.
"And I think the particular problem we have at the moment is that in the 1980s... the Americans recruited and trained Osama Bin Laden, taught him how to kill, to make bombs, and set him off to kill the Russians and drive them out of Afghanistan.
"They didn't give any thought to the fact that once he'd done that he might turn on his creators."
Mr Livingstone said Western governments had been so terrified of losing their fuel supplies that they had kept intervening in the Middle East.
He argued: "If at the end of the First World War we had done what we promised the Arabs, which was to let them be free and have their own governments, and kept out of Arab affairs, and just bought their oil, rather than feeling we had to control the flow of oil, I suspect this wouldn't have arisen."
He attacked double standards by Western nations, such as the initial welcome given when Saddam Hussein came to power in Iraq.
There was also the "running sore" of the Palestinian/Israeli conflict.
"A lot of young people see the double standards, they see what happens in Guantanamo Bay, and they just think that there isn't a just foreign policy," said Mr Livingstone.
Mr Livingstone said he did not just denounce suicide bombers.
He also denounced "those governments which use indiscriminate slaughter to advance their foreign policy, as we have occasionally seen with the Israeli government bombing areas from which a terrorist group will have come, irrespective of the casualties it inflicts, women, children and men".
He continued: "Under foreign occupation and denied the right to vote, denied the right to run your own affairs, often denied the right to work for three generations, I suspect that if it had happened here in England, we would have produced a lot of suicide bombers ourselves."
Mr Livingstone also criticised parts of the media for giving too much publicity to certain figures who were "totally unrepresentative" of British Muslims.
Mr Livingstone later took questions about the bombings from members of the London Assembly.
He said the unity shown by Londoners in the wake of the attacks was a commemoration to those who died and showed a determination not to give in to terrorism.
The mayor said most of the Tube would be working normally by the end of the week and the Underground should be working as before by the end of the month.
But he warned Tube users they would have to put up with the kind of disruption caused by packages left on trains which was seen during past IRA bombing campaigns.
There had been "very, very little" cancellations of existing hotel bookings and flights to London, said Mr Livingstone.
But there had been an immediate drop in new bookings for long-haul flights and hotels and a "dramatic reduction" in British people bringing children into the capital.
'Naming and shaming' hotels
Before this month's attacks, the levels of American tourists visiting London were only running at 75% of the numbers seen before the 11 September 2001 attacks in the US.
One way to counter the "turn down" in tourist trade was to attract more people from the UK and other parts of Europe, said Mr Livingstone.
Mr Livingstone said he did not have information about hotels raising prices for people trying to stay in London after the attacks.
But if there was evidence of "profiteering", the Greater London Authority would "name and shame" those hotels involved and refuse to do business with them in the future, he said.