Nigel Farage tied himself in knots over Ukip’s policy on sex education on Tuesday evening, as he denied knowledge of his party’s announcement two months ago that it would be scrapped in primary schools.

The Ukip leader made the comments in an ITV debate with young voters, who gave him a hard time over his party’s policies on immigration, his privately educated background, and the wealth of the party’s former treasurer.

In front of a small studio audience, Farage chose to discuss the issues of immigration, the European Union and democracy, while the young voters opted for the wildcard topic of education.

Asked whether Ukip would back compulsory sex education lessons and learning about gay relationships, Farage said “yes” as part of a proper “rounded” curriculum. This aligns him with Labour, rather than the current government position.

When it was pointed out that Ukip’s website advocates banning sex education in primary schools, he said: “I have never advocated that policy … I know there was a debate about sex education for 4-year-olds and whether that was appropriate, but I don’t think the age 11 was ever mentioned.”

In fact, it was announced in a speech by Ukip deputy leader Paul Nuttall in Doncaster at the party’s conference in October. He later tweeted that he had missed the beginning of Nuttall’s speech and it was indeed Ukip policy.

The Department for Education currently recommends that all primary schools should have a sex and relationship education programme tailored to the age and the physical and emotional maturity of the children.

The first half of the debate was dominated by immigration, with one young black audience member saying he thought it was “dangerous” for Farage to be turning his back on immigrants.

The Ukip leader said his party is more representative than the others and immigrants from outside the EU such as engineers from New Zealand face discrimination compared with low-skilled EU immigrants.

Another audience member asked him about comments he made about potentially feeling concerned about living next door to a group of Romanians.

“You’d be concerned about a group of men of any nationality moving next door,” he said.

The Ukip leader also said his predictions for how many Romanians and Bulgarians would migrate to Britain would prove to be correct.

Asked about Ukip members repeatedly making racist or homophobic jokes, Farage said there needed to be “more humour in politics” and argued other parties are not scrutinised to the same degree over their comments.

He was also challenged about his privately educated background, as the leader of a party that claims to be anti-establishment.

Farage, who was a metals trader in the city, said the young voter, who also asked about immigration, had obviously wound himself up and “needed to get some accuracy”.

“I’ve never worked on Wall Street, I’ve never been a stockbroker. I don’t think our party has ever taken money from a bank … I went to a private school, but have a look at the background of our 24 MEPs and how many of our people who are genuinely working class.”

The Ukip leader later hit out at those with a worrying “anti-rich attitude” after one audience member held up a picture of a mansion belonging to Ukip donor and former treasurer Stuart Wheeler, who is an Eton and Oxford-educated ex-Conservative millionaire.

“He’s not our treasurer. He’s never been – he’s not – an investment banker. He made his money out of a very entrepreneurial concept of spread-betting which has caught on and become a global thing. He has been a director of Amnesty International for many, many years … You are trying to portray this man who has been a success and made some money as being stereotypical of the establishment when he is not stereotypical of the establishment. Yes he did give the Conservatives money. He is one of our backers … I find this anti-rich argument quite worrying”.

Asked at the end whether he had met Richard Desmond, the owner of the Express newspapers, to discuss his papers supporting Ukip in return for a potential seat in the Lords, Farage said he would not comment on a private meeting.

• This article was amended on 3 December 2014 to correct a quote from Nigel Farage.