Nick Clegg has said Ukip leader Nigel Farage's mask is beginning to slip, and that "behind the beer-swilling bonhomie is a really nasty view of the world" and of modern Britain.

The deputy prime minister made the comment as he urged those opposed to divisive politics to vote against Ukip in European and local elections this week. At the same time a YouGov poll showed that the balance of those questioned who think Farage is doing a good job has fallen from +25 six weeks ago to +8, still good for a British party leader.

Clegg's remarks were prompted by Farage's claim last week that he would not want Romanians to be his neighbours in London, but that Germans would be different – Farage is married to a German woman. Clegg said the Ukip leader was offering the politics of division, which should have no place in modern Britain.

The Labour leader, Ed Miliband, who has stepped up his campaigning on the issue of immigration, accused Farage of a "racial slur" against Romanians, but said he did not believe the Ukip leader was a racist.

On BBC1's Andrew Marr programme, Clegg was asked whether Farage was a racist and said: "I think the mask is starting to slip and what has been revealed behind that beer-swilling bonhomie is a really nasty view of the world. Anyone who singles out one community or nationality and says 'I don't want to live next to them' – I think that is the politics of division, and I don't think it has any place in modern Britain."

Ukip moved to qualify its attitude to Romanians. Speaking on the BBC's Sunday Politics the party's Suzanne Evans said: "If 10 Romanian men moved in next door to me I think I'd certainly want to ask questions, and that's obviously very different from, say, a Romanian family moving in next door. If 10 Romanian men moved into me I'd think are they being ripped off by an unscrupulous landlord? In which case I'd be concerned. I'd think are they up to no good? In which case I'd be concerned."

With all political leaders stepping up their campaigning before Thursday's elections, the polls failed to show any consistent pattern, except that the Liberal Democrats are in danger of losing all their MEPs.

Clegg predicted that his party would hold to its course after the European elections, dismissing suggestions that there would be a challenge to his leadership or calls to quit the coalition. He said it would be self-defeating for the party to lose its nerve just when its policies were being vindicated. "Most Liberal Democrats are immensely proud of our resilience and our unity, and that despite the endless breathless predictions that we are seeing again right now we have delivered." He said he had lost count of the number of predictions of the government falling apart.

Clegg added: "In those areas where we were able to get our message across, knocking on doors, explaining what we have done, we will do better than people predict." Elsewhere he said the results would be "very, very challenging", but he disputed that this would have implications for the general election.

He said he was not a pollster or soothsayer, but claimed: "One of the things that the Westminster-based media has not picked up at all is the huge blow to traditional Labour support in the traditional Labour heartlands in the north at the hands of Ukip." He also accused the Conservatives of running a "hokey-cokey" strategy over renegotiation on the European Union.

The Tory minister Michael Fallon indicated on Friday that the party would campaign to leave the EU in a potential referendum in 2017 if it was unable to secure its programme of reform.

However, Clegg accused the Tories of "hithering and dithering" in their attitude towards the EU. "I think it's a sort of elevated form of petulance to say 'we're going to stamp our little feet to get our little short shopping list of really rather minor changes' – by the way, which they're now advocating – and 'if we don't get them then we'll quit'."

In an interview on the Murnaghan programme on Sky News on Sunday, Miliband condemned Farage's comments on Romanians, saying: "I think his remarks were deeply offensive … I think they were a racial slur but I don't think of Nigel Farage as a racist himself. They were inappropriate, and wrong, and he should not have made them."

Miliband has stepped up his campaigning on immigration. Some senior Labour figures, both in the shadow cabinet and in the so-called Blue Labour movement, are frustrated that the party has not done more to confront the Ukip threat earlier in the campaign.

The Conservatives' new culture secretary, Sajid Javid, said immigrants who came to live in Britain needed to learn English and to "respect our way of life". Javid, the son of Pakistani immigrants and the first Asian secretary of state, is likely to be a better conveyor of the Tories' tough line on immigration that some previous Tory spokesmen. He said people were entitled to expect immigrants to make a contribution to society.

"People want Britain to have more control over its borders, and I think they are right," he said in an interview with the Sunday Telegraph. "People also say, when immigrants do come to Britain, that they should come to work, and make a contribution and that they should also respect our way of life, and I agree with all of that. It means things like trying to learn English."