The director of a major US film about the 11 September terrorist attacks has called the UK inquiry into the 7 July bombings "pitiful" and "pathetic".
Paul Greengrass (centre) depicts one of the hijacked planes
British film-maker Paul Greengrass said that in the US after 11 September 2001: "No stone was left unturned to answer the question: what happened and why?"
But the UK had the Home Office's "paltry narrative" into the killing of 52 people by suicide bombers, he said.
United 93 is set on the hijacked plane that crashed in Pennsylvania in 2001.
Greengrass told BBC Radio Five Live: "In America, in response to 9/11 they mounted the 9/11 Commission which published a 400-page report, which held to account every arm of government including the CIA, the FBI.
"Here in this country we have a pitiful, pathetic response that says we cannot tell you the citizens of this country, we cannot tell you the victims of 7/7 about what happened and why."
The Home Office "narrative" and a report by the Commons Intelligence and Security Committee were both published earlier this month.
The "narrative" found the bombers were driven by "fierce antagonism to perceived injustices by the West against Muslims" and a desire for martyrdom, Home Secretary John Reid said.
The MPs' report found a lack of resources prevented security services from intercepting the men.
United 93 went to number two in the US box office chart
Politicians and relatives of the 52 people killed in the 2005 attacks have called for a full independent inquiry.
United 93 is the first Hollywood film about the 11 September attacks and has ignited a debate in the US about whether audiences are ready to see the day's events on cinema screens.
One New York cinema pulled the film's trailer after customers said they found it distressing.
It depicts passengers fighting back against their hijackers, leading to the plane crash in Shanksville, Pennsylvania.