Media playback is unsupported on your device Media caption Nick Robinson asks Nigel Farage about his German wife's job

On a day when Nigel Farage launched a nationwide poster campaign warning that millions of Europeans were waiting to take your job, I asked him why he employed a German as his secretary.

Couldn't he have found a British person instead, I wondered. Somewhat to my amazement the UKIP leader told me "nobody else could do that job".

His point, apparently, was that only his wife Kirsten - who as he often reminds us is German - would be prepared to work unsociable hours, seven days a week, helping him at "midnight, one o'clock, two o'clock".

As so often, the UKIP leader was trying to make me and all those listening smile along with him. He's an amusing and likeable guy and often I've done just that, but on this occasion I was determined to press on.

Mr Farage's decision to employ his wife at public expense highlights two important questions he and his party now face - about what their immigration policy means in practice and their attitude to public money.

'Sensible policy'

Mr Farage doesn't like questions about his MEPs' expenses - the £3,580 he gets from the EU every month to spend "as I see fit".

He refuses to put a total figure on the amount he's received from the EU, although a while back he said it was more than £2m. He insists that by employing his wife he is only doing what many Westminster MPs do.

As for immigration - the key issue which of his election campaign - Mr Farage is calling for a "sensible, open immigration policy" in which Britain would "re-claim control of her borders".

His goal is clear - to end the free movement of people in the EU - but the detail is much less so and is not spelt out in the party's European election manifesto.

I asked Mr Farage whether he was against all immigration. There could be zero, he said, before adding that, in a growing economy, "there is no doubt that selective immigration can be a beneficial thing to society".

When I pressed further, he said there was no reason a skilled Polish builder could not come here under UKIP policy, if there was a skill shortage to fill.

So, what numbers would be acceptable? Mr Farage was reluctant to say but eventually suggested that between 30,000 and 50,000 immigrants a year might be the right figure (compared with well over 100,000 net migration now).

One detail is clear, however. Under UKIP policy, Mrs Farage would be allowed to stay here and work.

Here's the full transcript of my questioning of Mr Farage on employing his wife:

Nick Robinson: You've warned about Europeans taking people's jobs. Your wife is German. She's your secretary. She's paid for by the British taxpayer.

Nigel Farage: Yes. She came here as a highly skilled person earning a high salary, paying a very large amount of tax. It all goes to show nobody must think….

NR: Is your wife taking someone else's job?

NF: No, because 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. And actually if you look at Westminster one in four MPs at Westminster, all right, employs a close family relative, and actually what's happening in the last two weeks, of the 73 British MEPs I'm the one that is being singled out and saying "Goodness me, Mr Farage, you're costing the taxpayer a great deal of money." Don't forget, I am the turkey that will vote for Christmas. I want to get rid of British MEPs and all the expenses.

NR: You see, you try to turn everything into a joke. You have a campaign which says Europeans are taking British jobs. You employ a German woman to work in your office. She happens to be your wife. She happens to spend many hundreds of thousands of British taxpayers' money. How do you justify that?

NF: No she doesn't. 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 flooding the lower end of the labour market.

NR: Why hasn't she taken a British person's job?

NF: Because nobody else could do that job.

NR: No British person could work for you as your secretary?

NF: Not unless I married them

NR: You don't think anyone's capable of doing that job?

NF: What, of marrying me?

NR: No. Of doing the job of your secretary.

NF: I don't know anyone who would work those hours, no.

NR: So that's it. It's clear - UKIP do not believe that any British person is capable of being the secretary of their leader?

NF: That's nonsense and you know it.

NR: You just said it!

NF: I said I need someone who can help me work at midnight, at one, two o'clock in the morning, unsociable hours. For seven years she did the job unpaid, for the last few years she's done the job on a monthly salary and from May she'll be doing it unpaid again.