Former British Deputy Prime Minister John Prescott has revealed that the 2003 Iraq War was “illegal,” days after an inquiry into the war savaged Tony Blair, who was prime minister at the time.

Former British Deputy Prime Minister John Prescott has revealed his believe that the 2003 Iraq War was “illegal,” days after an inquiry into the war savaged Tony Blair, who was prime minister at the time.

Prescott, now a member of the House of Lords, said he would live with the "catastrophic decision" of Britain going to war, alongside the United States, for the rest of his life.

"A day doesn't go by when I don't think of the decision we made to go to war. Of the British troops who gave their lives or suffered injuries for their country. Of the 175,000 civilians who died from the Pandora's Box we opened by removing Saddam Hussein," he wrote in the Sunday Mirror.

On Wednesday, the Chilcot report returned a damning verdict on Britain's role in the US-led war, finding it joined the conflict before all peaceful options had been exhausted and that judgements about Iraq's capacities were "presented with a certainty that was not justified".

It also said the invasion was not the "last resort" action presented to parliament and the public, and there was no "imminent threat" from Iraqi dictator Saddam Hussein.

Prescott said Blair's statement that "I am with you, whatever" in a message to then US President George W. Bush before the invasion in March 2003, as revealed in the Chilcot report, was "devastating".

Prescott said he now agreed "with great sadness and anger" with former UN secretary general Kofi Annan that the war was illegal.

He also praised Labour part leader Jeremy Corbyn for apologizing on the party's behalf.

Prescott expressed his own "fullest apology," particularly to the families of British forces who died.

Blair has previously apologized for any mistakes made but not the decision to go to war. He insisted the war was right and the world was safer without toppled Saddam.

Some 150,000 Iraqi people were killed in the six years after British and American troops invaded, plunging the country into chaos and creating fertile ground for militant groups like ISIS.

A total of 179 British troops also died.