United Kingdom Independence Party leader Nigel Farage has defended the employment of his German wife Kirsten as his assistant, claiming "nobody else" could do the job.

Mr Farage, who was publicising an advertising campaign warning about immigrants from the European Union taking jobs in Britain, insisted his wife's position was a "very different situation".

He said that no one other than his wife would be able to work the unsociable hours the role demanded.

UKIP campaign posters will carry stark warnings that "British workers are hit hard by unlimited foreign labour".

Another says that 26 million people in Europe are looking for work, adding, with a picture of a finger pointing at the reader, "and whose job are they after?".

Challenged by the BBC about his wife's job, Mr Farage said: "I don't think anyone else would want to be in my house at midnight, going through emails and getting me briefed for the next day."

"She earns a very modest salary for working extremely unsociable hours for me and being available up to seven days a week.

"It's a very different situation to a mass of hundreds of thousands of people coming in and flooding the lower end of the labour market."

Asked why he did not believe Mrs Farage had not taken the job of a British person, the UKIP leader said: "Because nobody else could do that job."

Mr Farage added that although his wife had been on a monthly salary "for the last few years", she would be unpaid from May.