Crispin Black, author of 7-7: What Went Wrong, says failure to address the country's intelligence shortcomings will "make it more likely that we're going to be hit again".
"I don't think that all terrorist attacks are discoverable or deterrable," Black told reporters before the book's publication on Friday. "But I feel strongly that 7/7 was discoverable and deterrable."
Black, a former military intelligence officer who advised the British government's cabinet Office for several years, praised the response of Londoners and the emergency services on the day of the attacks.
Fifty-six people were killed - including four suicide bombers - and more than 700 were wounded in explosions on three subway trains and a bus during the morning rush hour.
But he accused the government of adopting the attitude that Britain "had done everything it could do to prevent such attacks".
In fact, Black claimed, several signals were missed. He said Mohammad Sidique Khan, the bombers' presumed ringleader, had been investigated by the security services in connection with an alleged truck bomb plot that was thwarted in 2004.
Britain's MI5 intelligence service reportedly did not find Khan to be a threat to national security and failed to put him under surveillance.
Saudi Arabia warned the UK of
an impending attack
The government has declined to comment on the claim, which has been widely reported and backed up by intelligence experts.
Black said both the French and Saudi security services possessed intelligence that an attack on London was being planned.
French sources "had produced an assessment which suggested strongly that a bomb plot against the UK would emerge from small pockets within the home-grown Pakistani population", Black said. Three of the four bombers were Britons of Pakistani descent.
It was unclear whether the French information was passed on. After the bombings, Saudi officials said they had warned Britain last December of a planned summer attack.
"Why had we got these things so wrong when nearly everybody was expecting an attack?" Black asked.
The book blames "group-think" within government and intelligence services, which blinded them to the dangers of Britain's "covenant of security" - the much-criticised policy, dubbed "Londonistan" by its opponents, of allowing Muslim hardliners relatively free rein on the understanding that Britain would not be attacked.
Similar group-think has prevented authorities from acknowledging that the Iraq war has increased the risk of terrorist attack in Britain by radicalising a small number of young Muslims, he said.
Black, who says he supported the war at the time, said it was now clear that "the Iraq war, far from extinguishing terror, may have encouraged it".
"Whatever the failings in the run-up to 9/11 ... the Americans were ruthless on themselves. We're patting ourselves on the back"
Prime Minister Tony Blair has repeatedly rejected the idea of a link between the bombings and the presence of British troops in Iraq.
The House of Commons Intelligence and Security Committee is looking into the 7 July attacks. But Black said Britain needed a public inquiry similar to that of the 11 September commission in the United States after the 2001 attacks in New York and Washington, DC.
"Whatever the failings in the run-up to 9/11 ... the Americans were ruthless on themselves," he said. "We're patting ourselves on the back.
"It's like Alcoholics Anonymous. Unless you admit, internally and externally, that it was a poor performance, you're not going to get better."