Senator Carl Levin of Michigan said Tenet presented false information to the UN during public hearings about all the top suspected weapons of mass destruction sites in Iraq before the war.
The senior Democrat on the Senate Armed Services Committee and a member of the intelligence committee, Levin added he could "only speculate as to Director Tenet's motive.
"All such [WMD] sites were not shared and Mr Tenet's repeated statements were false."
The CIA last month declassified the number of top suspected WMD sites categorised as high and medium priority, and acknowledged that 21 of those 105 sites were not shared with the United Nations before the war.
A US intelligence official countered that nine of those 21 sites had been "frequently" visited by UN inspectors between 1991 and 1999 and they knew as much about them as the CIA.
Three of the sites were added to the CIA's list after Iraq declared them to the United Nations, and three sites were duplicate entries.
The CIA did not know the precise locations of several other sites and efforts were being made to develop more data on them, the official said on condition of anonymity.
"In other words, honest answers by Director Tenet might have undermined the false sense of urgency for proceeding to war and could have contributed to delay, neither of which fit the administration's policy goals"
Democrat senator for Michigan
Reasons for war
Levin said if the public had known that not all WMD site information had been shared with UN weapons inspectors it might have reinforced sentiment that UN inspections should be completed before going to war.
"In other words, honest answers by Director Tenet might have undermined the false sense of urgency for proceeding to war and could have contributed to delay, neither of which fit the administration's policy goals."
The senator's comments come as the number of Americans who believe the Iraqi government of Saddam Hussein had weapons of mass destruction is declining, according to a Harris Interactive poll released Monday.
About 51% of those polled believed that Iraq had the banned weapons - a drop from 61% in mid-December following the capture of the former Iraqi dictator.
Some 40% of those polled did not believe Saddam had WMDs, up from 32% in December.
The US government of President George Bush launched a war on Iraq in March 2003 claiming Saddam had nuclear, biological and chemical weapons that posed an imminent threat to the United States.
US officials have said they based their policy on intelligence information provided by the CIA.
The poll, carried out among 1020 US adults in mid February, also found that 43% believed the US government "deliberately exaggerated the reports ... in order to increase the support for the war."