This year's Al Quds Day rally has prompted a strong response from Mayor Boris Johnson in anticipation of political rallies due to be held during the Olympic Games next year.

Although numbers for Sunday's Trafalgar Square rally, organised by the Islamic Human Rights Commission, were thought to be down on previous years, the level of vitriol remained distressingly high.

One of the biggest signs, paraded by a young boy, read: "For World Peace, Israel Must Be Destroyed." Next to him, his father's poster read "Israel Your Days Are Numbered", on the other side of which were the words "Committed Every War Crime In The Book, Yet The World Remains Silent, DEATH TO ISRAEL". It took two people to carry a huge sign, which read "The World Stopped Nazism, The World Stopped Apartheid, The World Must Stop Zionism". Many waved the yellow Hizbollah flag, or held up "We are all Hizbollah" signs, with a photo of two injured and crying Palestinian children.

One speaker said: "You can't take a terrorist nation's army and defeat it with a small group of sincere fighters. It needs some of those states around [Israel] to release their armies to burn that land and then that region will see peace like it had in the past under sincere Islamic rulers."

Lauren Booth, Tony Blair's half-sister-in-law, pledged her support for Hamas's "right to resist," saying: "It's time for Al Quds [Jerusalem] to be liberated for Islam and people of the world who wish to pray there to the one God. We say to you Israel, we see your crimes and we loathe your crimes. To us your nation does not exist, because it is a criminal injustice against humanity."

But on Wednesday a spokesman for Boris Johnson said: "The Mayor believes that intolerance of our fellow citizens and hate crimes against specific communities are totally unacceptable, particularly in a city like London and especially in 2012 when the eyes of the world will be on the capital. The Greater London Authority will not be authorising political rallies in Trafalgar Square during the Olympic and Paralympic Games."