Seema Takhar does not fit the normal stereotype of a Ukip voter. Nor is she very interested in politics most of the time. But when she hears what Nigel Farage's party has to say on the subject of immigration, it resonates.

It is midway through a weekday afternoon and Seema is busy dealing with clients in the beauty salon she runs in Havering, east London, when Lawrence Webb, a UK Independence party councillor, drops in with some local election leaflets. "Yes, immigration is a big issue for me here," she tells him, adding she will now consider voting for Ukip. "When our family came here in the 70s they got no help. We had to work for everything. It is all different now.

"Many of the immigrants today come and live on benefits and in council homes. Their children will live on benefits too because that is all they know. I don't think that is right."

Seema's mother Renu, who came to the UK in 1973 from Kenya (the family originates from India), walks into the salon and reinforces the message. Renu now works in a post office and says much of her time is spent sending "moneygrams" abroad for immigrants supporting families back home. "A lot of money is made here but is leaving the country. When we made money here it stayed in the UK," she says.

Webb, who became the first directly elected Ukip councillor in London in a byelection last year, refers loosely to such families as part of the "Windrush generation". They have been here for two or three generations, he says, have worked hard, done well, are part of the community and now, in many cases, find their children can't get work and have to compete for houses and places in schools with new immigrants from the EU. The result, says Webb, is that they are now turning for help to Ukip, which wants to end Europe's open borders policy.

If Farage's party – under sustained attack in recent weeks for being packed with racists – was only, or mainly, drawing its support from crusty old colonels in the shires who dislike multicultural Britain and metropolitan Tories such as David Cameron, it would not be proving so resilient in the polls. Something more complicated and deeper is going on.

Ukip is on the march because it is exciting interest from people across the spectrum, from disgruntled Conservatives certainly, but also from ex-Labour supporters, the generally disaffected, the hitherto politically disengaged, and longer-established immigrant families with socially conservative views. The party had no councillors in the borough of Havering until last year; it now has seven and Webb believes Ukip will be in coalition with the Tories and Labour after the local elections this month. "There is little doubt it will be in no overall control," he says.

Down the road in Barking and Dagenham, where Labour won every seat in 2010, there are equally surprising moves to Ukip. Four Labour councillors recently defected to Farage's party, including the first Asian to do so in the area, Tariq Saeed, who is a practising Muslim and proud to call himself British. Saeed told the Barking and Dagenham Post: "Ukip is not a racist party. Ukip is saying we aren't gaining anything while we are in the EU. We want to put the British people first."

Such backing from an Asian, Muslim, ex-Labour councillor suggests Ukip, though containing plenty of unfortunate types, now has a support base far more complex and varied than was the case in 2006 when Cameron dismissed the party as a "bunch of … fruitcakes and loonies and closet racists mostly". The past week has seen Ukip continue to defy the normal rules of politics, as more revelations about the bizarre and outrageous views of some of its members have coincided with opinion polls showing it going from strength to strength. On Wednesday its local election candidate William Henwood resigned from the party after the Observer revealed that he had suggested the comedian Lenny Henry should emigrate to a "black country". No sooner had Henwood taken his bow than one of Ukip's ex-donors, Demetri Marchessini, told Channel 4 News that he thought there was no such thing as marital rape and that women should be banned from wearing trousers because they "discourage love making".

Such outlandish comment has been all too easy for the media to uncover. The Tories hoped all this, and Farage's decision not to stand in the forthcoming Newark parliamentary byelection – which they said showed he was frightened – would finally puncture his party's bubble. But instead a ComRes poll found support for Ukip in the runup to the European elections on 22 May had shot up by eight points to 38% while support for Labour and the Tories had fallen by three points each to 27% and 18%.

Farage accused the media and the establishment parties of going for Ukip while failing to subject themselves to similar scrutiny. "So what is it about Ukip that makes it racist for us to talk about migration, but not the other parties? Could it be because we're not part of their club? It smacks of a cartel, trying to restrict entry into the market for new competitors. And I think it's one which will backfire on them."

On that he seems to be right, at least for now. With less than three weeks to go until the council and European elections, Ukip has taken over from the Liberal Democrats as the natural party of protest, hitting the Tory and Labour votes into the bargain. The Tories are resigned to coming third in the European elections behind Labour and Ukip. Their coalition partners, the pro-EU Lib Dems, face the potential loss of all 11 of their MEPs in the Strasbourg parliament, and are expected to lose 250 to 350 town hall seats.

Up and down the country Ukip is establishing local support in a way the Lib Dems – when untainted by power – used to. In pockets across the south-west, where Nick Clegg's party has traditionally been strong, Ukip is breathing down Lib Dem necks. In Stroud, in the Severn valley, the Lib Dems usually table a full list of candidates in council elections. This year just three Lib Dem candidates will contest the 18 seats up for election. Ukip, by contrast, is fielding 10, two of whom, Angie Lyes and Jim Simpson, have defected not from the Tories but from Labour.

Caroline Stephens, chairwoman of Ukip in Stroud, hopes her party will win its first council seats, possibly gaining as many as six. On the leafleting trail, she concedes that racist comments and gaffes by Ukip candidates have left her vulnerable to negative comments. In one shop on Friday afternoon, the proprietor greeted Stephens, saying: "Oh, it's the mad woman again." But he said he was likely to vote Ukip nonetheless.

Sir Graham Watson, the Lib Dems' only MEP in the south-west, admitted his chances of re-election next month were low and said that Ukip was sweeping up votes: "I think the Ukip vote is very strong. Ukip, in a sense, almost started here, in that this is the region in which they won their first European parliamentary seat. It's been going up since then." Gawain Towler, third on Ukip's European election slate, added: "The Lib Dems are a busted flush. If they think the south-west is one of the few seats they'll keep, on the ground it really doesn't feel that way. They are in real trouble."

In the north, Ukip threatens a similar disturbance to the old order. Edward McMillan-Scott, who defected to the Lib Dems from the Tories in 2010 and is now one of two Lib Dem MEPs in the region, says his chances of extending his 30-year stay in the European parliament are on a knife edge. "It is very tight. If I don't do it, it will be because of Ukip," he says.

With local and European election day fast approaching, and a year until the general election, the established parties have not found a way to knock Ukip off its perch. Farage's party seems to be thriving and widening its base, and its message on immigration and Europe is more popular than its opponents dare to admit. The Tories seem confused. They want Ukip voters back but seem locked into a strategy of insulting the party to which they have defected in the meantime. At the Conservative party's European election launch on Friday, Cameron said: "I don't need to discredit Ukip – they do a good enough job themselves."

Across the road from Seema Takhar's Pink Salon in Havering, another local business owner says he is no longer bothered by what Cameron says. He too is thinking of voting Ukip because he is fed up with all the others. It is the parties that have wielded power, not Ukip, that are discredited. "I have seen Tories and Labour have power and not seen any difference," he says. "They don't do what they say."