LONDON (Reuters) - The UKIP party will likely top European elections on Thursday or come a close second, according to opinion polls that suggest a barrage of criticism accusing it of racial slurs and bigotry has failed to put off voters.
All three of Britain's three main political parties have strongly criticised the UK Independence Party (UKIP), which wants Britain to leave the European Union and to impose much tougher immigration controls, prompting the party to take out an advert in a national newspaper to assert that it is not racist.
Large swaths of the press, including tabloid The Sun newspaper, owned by Rupert Murdoch's News Corp., have joined the fray. This week, The Sun asked readers whether they thought UKIP leader Nigel Farage was a "bigoted menace".
But two polls published on Wednesday, on the eve of the European vote, the last major political test before a national election next year, suggested the sustained criticism was not deterring UKIP supporters.
One poll, by YouGov for The Sun, had UKIP tied with the opposition Labour party on 27 percent, placing Prime Minister David Cameron's Conservative party on 23 percent. When only those who were certain to vote were counted, YouGov said UKIP had a 5 percentage point lead.
A second poll for The Daily Mirror by Survation also had UKIP tied with Labour, this time on 29 percent. But again, when it took into account likelihood to vote and awareness of the vote, it credited UKIP with a 5 percentage point lead.
"UKIP voters told Survation they are both more likely to vote and more aware of the date of Thursday's European election" than supporters of the other parties, the pollster said.
In both polls, the Liberal Democrats, Cameron's pro-European junior coalition partner, were placed fourth.
Writing for the right-leaning Daily Express newspaper, Farage said the barrage of criticism had backfired.
"I think, ironically, it has made those who support us even more likely to stick with us in subsequent elections," he wrote.
Final results of voting will be available only on Sunday evening, after polls for the European Parliament close in Italy.
Polling has shown that UKIP has siphoned support from all three main parties by tapping into discontent about the ability of politicians to effect change, particularly on immigration, which many Britons perceive to be overly high.
Immigration has joined the economy at the top of voter concerns for the first time in years after EU restrictions on Romanians and Bulgarians working in Britain were lifted at the start of the year.
UKIP has leveraged concerns about higher immigration from the two poor east European nations to argue that the only way Britain can control its borders is by leaving the European Union to cut loose from the bloc's freedom of movement rules.
But Farage, a fast-talking former commodities trader, has courted controversy by saying that people living in London would be worried if a group of Romanian men moved in next door because of high crime rates among such newcomers.
Three prominent Labour lawmakers accused him of being a racist after he made the comments in a radio interview, prompting him to take out a full-page advert in a national newspaper asserting his party was not racially prejudiced.
In media interviews on Wednesday, Farage predicted UKIP would win the European elections and could go on to hold the balance of power after a national election in May 2015.
Britain's first-past-the-post voting system for national elections, which differs from the proportional representation used for Thursday's vote, is likely to make that difficult.
Farage said he would be willing to support either a Conservative or Labour government if it meant he could secure a referendum on Britain leaving the European Union.
The Conservatives are promising such a vote by the end of 2017 if re-elected. Labour says it is unlikely to hold such a vote if elected and would only do so in the event of a new significant transfer of powers to the EU bloc.
Editing by Jon Boyle