LONDON (Reuters) - A poster designed to encourage ethnic minorities to vote in next month’s European Union membership referendum sparked fierce criticism on Thursday as figures on both sides of the EU debate objected to the depiction of an aggressive white man berating a elderly Asian woman.

A woman holds a Union Flag shopping bag in London, Britain April 23, 2016. REUTERS/Kevin Coombs/Files

Under the slogan ‘A Vote is a Vote’ two figures are pictured evenly balanced on a seesaw. One is a woman of south Asian origin wearing a sari, the other is shouting, pointing at her, and dressed to look like a ‘skinhead’ - a subculture dating back decades and often associated with racist violence in Britain.

The striking tableau is the latest attempt to engage voters in the debate over Britain’s future ahead of the June 23 referendum, in which public opinion is evenly split and many remain undecided about how to vote, or whether to vote at all.

The ad will run on billboards across London and Manchester. It was designed by advertising firm Saatchi & Saatchi to promote ‘Operation Black Vote’ - a campaign to encourage black and ethnic minority Britons to register and vote.

“My concern is it just reinforces stereotypes,” said London’s newly elected mayor Sadiq Khan, the city’s first Muslim leader.

“Lots and lots of Londoners, some of my best friends who are white, don’t behave that way. I’ve got aunties and friends who are Asian and they don’t seem scared. I’m not sure what their motivation is with those particular images.”

Operation Black Vote said around 30 percent of Britain’s 4 million black and ethnic minority citizens are not registered to vote, and many who are choose not to cast their ballot.

Earlier this month, a survey of more than 22,000 Britons found that white voters were divided evenly on the EU issue but opinion among ethnic minority groups was split by 2 to 1 in favour of staying in the 28-nation bloc, putting the “remain” camp ahead by 43 percent to 40.5 percent.

However, once the results were filtered to only include those very likely to vote, the result changed to 45 percent backing an exit and 44.5 percent wanting to stay.

Immigration, which rose to a net 330,000 people in 2015, data showed on Thursday, is one of the central and most emotive issues in the debate over whether Britain should leave or stay in the 28-country bloc, and has featured heavily in the ‘Out’ campaign.

But Khan, who set out a pro-EU argument in a speech in London on Thursday, was joined in criticism of the advert by Nigel Farage, leader of the UK Independence Party and one of the figureheads of the campaign to leave the EU.

“I want to engage people in all communities to get involved in our democracy but I’m afraid this poster is a really big mistake,’ he said. He called the image a disgusting example of sectarian politics.

Operation Black Vote defended the poster, saying it was deliberately designed to draw attention to race issues that have surfaced during the campaign.

“Many people feel that this debate, whether it’s the Remain or the Leave camps, has been characterised by anger, not much objective information, and at times the demonisation of foreigners and in particular people of colour,” the campaign said in a statement.