Veteran Labour politician Tony Benn has shared the stage with east London Respect MP George Galloway at an international peace conference.
Mr Benn said this peace movement was the biggest in his lifetime
Speaking to up to 1,500 anti-war protesters and activists, Mr Benn condemned the conflict in Iraq as "illegal, immoral and unwinnable".
The event at the Royal Horticultural Hall in central London was organised by the Stop the War Coalition.
Convenor Lindsey German hopes to find ways to progress the peace movement.
"This is a day of people coming together to talk about how we can take the troops out of Iraq and allow the Iraqi people to run their country," she said.
The morning was dominated by Mr Benn's speech, in which he said the current peace movement calling for troops to be withdrawn from Iraq was "the biggest in my lifetime".
"It represents 60% of US opinion now and the same in Britain. It is a very positive movement and has support right across the political spectrum."
Meanwhile George Galloway said the people of London were saying they are not part of this war.
The MP for Bethnal Green and Bow is often embroiled in controversy.
On the day after the July bombs, he said Londoners had paid the price for Iraq and Afghanistan - comments described by a government minister as disgraceful.
Fellow speakers included Cindy Sheehan, the mother of a US soldier killed in Iraq, speaking on behalf of Gold Star Families for Peace, and Reg Keys for Military Families Against the War, who also lost his son, a military policeman, in Iraq.