Jeremy Corbyn has said Labour is "united"' in fighting anti-semitism and racism "in any form" in a speech at a May Day rally in central London.
Addressing thousands of people from the top of a red London bus, Mr Corbyn told the crowd that had gathered at Clerkenwell Green to celebrate the international day honouring workers, that Labour's strength lay in its diversity.
"We stand absolutely against anti-semitism in any form. We stand absolutely against racism in any form," he said.
"We stand united as a Labour movement, recognising our faith diversity, our ethnic diversity and from that diversity comes our strength. That is the strength of our movement."
Mr Corbyn also used the speech as an opportunity to bolster Labour's mayoral candidate Sadiq Kahn, who has warned his party's mishandling of the anti-semitism row could harm his chances at the polls.
Many say Mr Corbyn has acted too slowly to quell the row.
Earlier Diane Abbott, Labour's shadow international development secretary, defended Labour and Mr Corybn saying any suggestion Labour had a "problem" with anti-semitism was a "smear".
Mr Corbyn also used his May Day speech to criticise attitudes towards refugees and immigrants, saying: "We're more interested in blaming immigrants, victims of war who are refugees, than facing up to the realities that we are all human beings living on one planet."
His appearance marks the first by a Labour leader at a May Day rally in 50 years.
Ahead of Mr Corbyn's speech Frances O'Grady, general secretary of the TUC, wished the crowd a happy May Day and sent a special message of solidarity to BHS workers, saying: "We stand by you."
Crowds carried placards with slogans such as "Cameron must go" as the rally marched on to Trafalgar Square.