Tony Blair has called the manner of former Iraqi leader Saddam Hussein's execution "completely wrong".
But the prime minister, who has not previously spoken publicly on the death, said the punishment "should not blind us" to Saddam's crimes.
Mr Blair has been under pressure to comment after several senior colleagues criticised last month's execution.
It was important not to "lurch into a position of forgetting" Saddam's victims, he told a press conference.
At the weekend, Chancellor Gordon Brown described the manner of Saddam's hanging as "deplorable and unacceptable", echoing comments by several senior government ministers.
Mobile phone footage shows the former Iraqi leader - a Sunni - being taunted with Shia slogans before his death.
Mr Blair's spokesman has already called the manner of the execution "completely wrong", but this is the first time the prime minister has criticised it in person.
Mr Blair told a Downing Street press conference: "As has been very obvious from the comments of other ministers and indeed my own official spokesman, the manner of the execution of Saddam was completely wrong.
"But that should not blind us to the crimes he committed against his own people, including the death of hundreds of thousands of innocent Iraqis; one million casualties in the Iran-Iraq war, and the use of chemical weapons against his own people, wiping out entire villages of people.
"So the crimes that Saddam committed do not excuse the manner of his execution, and the manner of his execution does not excuse the crimes.
"Now I think that's a perfectly sensible position that most people would reasonably accept".
Liberal Democrat leader Sir Menzies Campbell has previously said Mr Blair's "unwillingness to condemn the shameful scenes surrounding Saddam Hussein's execution does him no credit".
Saddam was executed last month following his conviction in November over the deaths of 140 men in the town of Dujail in 1982.
Mr Blair's comments come after footage taken of Saddam's dead body appeared on the internet.