WASHINGTON — A stinging report by the Senate Intelligence Committee released Wednesday concluded that the attack 16 months ago that killed four Americans in Benghazi, Libya, could have been prevented, singling out the State Department for criticism for its failure to bolster security in response to intelligence warnings about a growing security crisis around the city. 

The report is broadly consistent with the findings of previous inquiries into the attack on Sept. 11, 2012, but it is the first public examination of a breakdown in communications between the State Department and the C.I.A. during the weeks leading up to the deadly episode at the diplomatic compound where J. Christopher Stevens, the American ambassador, died. 

It is also the first report to implicitly criticize Mr. Stevens, raising questions about his judgment and actions in the weeks before his death.  Like previous inquiries, the Senate investigation does not cite any specific intelligence warnings about an impending attack. 

The events in Benghazi and their aftermath became the subject of a fiercely partisan debate, with Republicans accusing Obama administration officials of making misleading statements about connections between the attackers and Al Qaeda.  In an addendum to the bipartisan report, Republican committee members singled out former Secretary of State Hillary Rodham Clinton, a possible Democratic presidential candidate in 2016, as bearing ultimate responsibility for lax security at the diplomatic compound in Benghazi.