Britain’s Home Office has not released the findings of its inquiry into the July 7 bombings of London’s subway and bus system, which killed 56 people, including the four Muslim attackers.

But The Observer newspaper said in a front-page story yesterday that initial drafts of the government’s findings, which it has obtained, say the US-led Iraq war was a key “motivating factor” for the attackers and that it helped to radicalize them. Other factors included economic deprivation, social exclusion and a disaffection with society in general, including community elders, the paper said.

The inquiry confirms that two of the four British attackers, Mohammed Sidique Khan and Shehzad Tanweer, had traveled to Pakistan before the attacks and met with Al-Qaeda operatives, The Observer said.

Such findings would corroborate suspicions about Khan, the ringleader of the bombings, that were raised by a farewell videotape he had made and which was shown on Al-Jazeera television after the July 7 violence.

It was broadcast alongside a video of Al-Qaeda’s No. 2, Ayman Al-Zawahri, warning of more attacks.

In Khan’s video, he urged fellow British Muslims to take part in a jihad, or holy war, against their enemies.

“Our so-called scholars today are content with their Toyotas and their semidetached houses,” said Khan, 30, who was born in Pakistan but raised in the British city of Leeds.

“If they fear the British government more than they fear Allah, then they must desist in giving talks, lectures and passing fatwa’s, and they need to stay at home — they’re useless.”

He also said, “Your democratically elected governments continuously perpetuate injustice against my people all over the world, and your support of them makes you directly responsible, just as I am directly responsible for protecting and avenging my Muslim brothers and sisters.”

Khan said Prime Minister Tony Blair “not only disregards the millions of people in Iraq and Afghanistan, but he does not care about you as he sends you to the inferno in Iraq and exposes you to death in your land because of his crusader war against Islam.”

Asked about The Observer’s report, the Home Office issued a statement yesterday saying the results of its inquiry will be published soon, but that it would not discuss them beforehand.