Senior Labour Party figures are fighting back against charges there is anti-Semitism in the party's ranks ahead of Thursday's vote for a new mayor of London.

Labour legislator Diane Abbott says Sunday the party is being smeared by its political enemies while union leader Len McCluskey says the controversy is being exploited by Labour's rivals.

Labour's mayoral candidate Sadiq Khan has conceded the anti-Semitic issue has made his election campaign more difficult in the final days before the vote.

The row intensified days ago when former London Mayor Ken Livingston was suspended from his senior Labour Party post after asserting that Adolf Hitler had been a Zionist before he went mad and launched the Holocaust. Livingstone spoke while defending a Labour Party legislator who had been suspended for anti-Semitic posts.