Tony Blair is expected to say that the manner of Saddam Hussein's execution was "completely wrong" when he breaks his silence on the issue.
Chancellor Gordon Brown added his voice to the chorus of criticism over the execution of the former Iraqi dictator, denouncing the way in which it was handled as "deplorable" and "completely unacceptable".
Mobile phone footage of Saddam being taunted as he was led to the gallows sparked outrage around the world when it appeared on the internet.
But Mr Blair has so far resisted mounting pressure to respond, saying only that he would make a public comment in the course of the coming week.
No 10 said he would use the opportunity to express his concern about the way the hanging was conducted and to voice his support for the Iraqi government's investigation into how it came to be filmed.
"In terms of what he will say, we don't think there are going to be any surprises on where he stands," said a spokeswoman. "He supports the inquiry by the Iraqi authorities. He does believe that the manner of execution was completely wrong, but this shouldn't lead us to forget the crimes that Saddam committed, including the death of hundreds of thousands of Iraqis."
Mr Brown's denunciation of Saddam's hanging echoed the comments of Deputy Prime Minister John Prescott, who said that the way it was done was "deplorable" and those responsible should be "ashamed".
Health Secretary Patricia Hewitt also described Saddam's treatment as "very shocking" while industry minister Margaret Hodge said she "abhorred" the way his death sentence was carried out.
Mr Brown told BBC1's Sunday AM: "Now that we know the full picture of what happened, we can sum this up as a deplorable set of events. Even those people, unlike me, who are in favour of capital punishment found this completely unacceptable and I am pleased that there is now an inquiry into this and I hope lessons in this area will be learnt, as we learn other lessons about what has happened in Iraq."
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Mr Brown acknowledged that mistakes had been made in the handling of Iraq following the 2003 war, and did not rule out a future inquiry into what went wrong.
