Lizzy Vaid, an events manager for the party and assistant to the leader, has appeared in a variety of promotional documents portraying her as a grassroots supporter.
In Ukip’s manifesto for forthcoming European and local elections her picture is captioned simply “Lizzy Vaid, Devon”.
“I’ll be voting Ukip because they are the only party listening to what people want,” she is quoted as saying.
Asked about the labelling during an interview with Sky News, Mr Farage said he “did not see the need” to state that she was an employee.
“I don’t see any reason to do that at all,” he said. “She is someone in our promotional material who is going to vote for Ukip, she joined Ukip, she got a job with Ukip, because she believes in what we stand for.
“Do you want us to say the religion of all our candidates?”
Mr Farage said Ms Vaid was a “member of our party and has been for some years”.
“She works for us in our head office in London,” he added. “I don’t think you would ask this question of the Labour Party or the Liberal Democrats or the Conservatives. The fact that Lizzy Vaid is half Indian and works for us is as far as we are concerned a non-issue.”
The party leader said rivals were “screaming blue murder” over campaign material because they did not want to have an “honest conversation” about immigration.
The robust defence came after religious figures joined MPs in condemning the images, funded with £1.5 million from millionaire ex-Tory donor Paul Sykes.
It is Ukip’s biggest ever publicity drive, as the party aims to achieve a “political earthquake” by topping the polls on May 22.
Cardinal Vincent Nichols, the leader of the Catholic Church in England and Wales, said it was wrong to use expressions that suggest “dismay or distress at all these people coming to this country”.
Tory backbencher Nicholas Soames posted on Twitter: “At a time when our country really needs to come together, the Ukip advertising campaign is deeply divisive, offensive and ignorant.”
Labour MP Keith Vaz, chairman of the Commons Home Affairs Select Committee, said: “Ukip have lowered the tone of the European debate with these spiteful and inaccurate claims on immigration which seek only to divide communities.”
But Mr Farage told the BBC: “The fact that Westminster hate it and want to scream blue murder over it is because they have opened up the doors, they have fundamentally changed the lives of millions of people and they would rather we did not talk about it and just brush it under the carpet.”