A survivor who was imprisoned and sent to Auschwitz for her efforts to resist the Nazis has warned against comparing the Holocaust with other atrocities.

Anita Lasker-Wallfisch, 84, was the main speaker at Tuesday's Holocaust Memorial Day ceremony at City Hall, hosted by London Mayor Boris Johnson.

Mrs Lasker-Wallfisch was sent to Auschwitz after her work forging documents for prisoners of war was discovered. A talented cellist who became a professional musician in Britain after the war, she escaped the gas chambers because the camp's orchestra needed a cellist. She was then in Bergen-Belsen, the liberation of which, on April 15, 1945, came "in the nick of time".

She said Auschwitz "has become a symbol of the abject depravity to which humans can sink. No one of us was meant to survive that - some of us did but it was pure luck."

Mrs Lasker-Wallfisch noted the tendency to equate the Holocaust with violent episodes in history, based on fighting for territory or power.

"Believe me, this is not a competition for first place," she said, but added: "We must be careful about what makes this different from all other genocides.

"This was just simply premeditated mass murder of the innocent, who were brought from all over for this. It was racism carried to the extreme."

Yet the world had learned "precious little" from its lessons, she added.

"Holocaust Memorial Day is not just about the past, it is also about the future and the fervent hope that similar tragedies will never happen again - and that when we speak up and speak out, there will be enough people who are listening."

The ceremony also featured a cello performance from Mrs Lasker-Wallfisch's grandson Abraham Jacobs-Wallfisch.

This year's HMD theme, Speak Up, Speak Out, was addressed by Rabbi Dr Abraham Levy, head of the Spanish and Portuguese Jews' Congregation. "We remember the cruelty that man can inflict on his fellow man," he said, "but do not forget the acts of bravery of men and women of other faiths who risked their lives to save innocent men and women. "At a time when Nazi ideology is again rearing its ugly head, we remember with thanks the brave behaviour of decent God-fearing people of all faiths."

Mr Johnson read survivor Primo Levi's haunting poem Shema, an appeal for people to be aware of the suffering of others.