Supporters of the right-wing party rose to their feet and others jeered as Christopher Hope of the Daily Telegraph questioned Nigel Farage on the manifesto’s lack of diversity.
Ukip officials reportedly did not interrupt the heckling, and Nigel Farage can be seen to applaud.
The picture in question is of Ukip's overseas aid spokesperson, Nathan Gill MEP, posing pointedly with a woman wearing African dress. It is on page 68 of the manifesto. Ukip's policy is to sharply cut overseas aid.
In a video from the scene, Ukip supporters of Asian ethnicity can be seen rising to their feet and shaking hands with other Ukip supporters, apparently in response to the question.
The incident recalls an earlier 2013 fracas in which then-Ukip MEP Godfrey Bloom struck Channel 4 journalist Michael Crick with a copy of his manifesto after he was asked a similar question.
Mr Bloom said Mr Crick was "racist" for asking the question.
Ukip argues that it is not racist or xenophobic to stop people from coming to the UK because of where they were born.
42 per cent of the party’s supporters admitted to being “a little prejudiced” while 6 per cent said they were “very prejudiced” – a total of 48 per cent.
The proportion of Ukip voters admitted to the charge is significantly higher than that in the general population, according to the poll.
Last month party leader Nigel Farage sparked a race row by saying that legislation preventing racial discrimination in the workplace should be scrapped.
Asked specifically if Ukip would retain laws against discrimination on the grounds of race or colour, he replied: “No, because … we as a party are colour-blind.”
Ukip gaffes and controversies
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Mr Farage said last year that parts of Britain had become like a “foreign land” because of immigration.
“In scores of our cities and market towns, this country in a short space of time has frankly become unrecognisable,” he said.
Ukip’s manifesto was launched in the party’s target seat of Thurrock, Essex, today.
The party leader told his audience that Ukip were “the only party with the self-confidence and belief in this nation”.
“Ordinary people have been left behind and they have simply got nobody to speak for them,” he told his audience at the Thurrock Hotel.
The party’s manifesto pledges a fast referendum on Britain's European Union membership, controls on immigration, recall powers for MPs, increased NHS spending and to take minimum wage earners out of tax.
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