He predicted the party was on course for the “biggest political shock” for years by beating Labour and the Tories to win the largest number of votes at the contests on May 22.

Mr Farage also told activists at the Ukip spring conference that it was well placed to build a base in local government by picking up hundreds of seats in council elections on the same day.

But the conference launch was undermined by the disclosure that its new slogan “Love Britain” had previously been used by the BNP. A spokesman insisted Ukip was “reclaiming” the words from the far-Right party.

In his keynote address in Torquay, Mr Farage seized on figures this week showing a surge in net migration – mainly fuelled by the arrival of European Union workers – as evidence that Britain’s frontiers were under unprecedented pressure.

In provocative remarks, he argued that communities across the country had irreparably altered as a result of mass immigration and were not fit to pass on to future generations.

“In scores of our cities and market towns, this country in a short space of time has frankly become unrecognisable.

“Whether it is the impact on local schools and hospitals, whether it is the fact in many parts of England you don’t hear English spoken any more.

“This is not the kind of community we want to leave to our children and grandchildren.”

He argued: “Eighty per cent of us in this country believe open door immigration is irresponsible, against the interests of the people in this country and that it must stop.”

Mr Farage claimed Britain now had a “totally distorted labour market because of the massive oversupply that has come to us from eastern Europe”. And he added: “It is ordinary folk, it is ordinary families that are paying the financial price.”

The Ukip leader was speaking after a year in which the party has achieved a series of strong by-election performances, consistently outscored the Liberal Democrats in opinion polls and picked up nearly 150 local council seats.

He told the conference that the party represented the biggest threat to the political mainstream for a generation.

He added: “Our ruling classes have lost confidence in this country and that is why they have sold us out and it has cost us money, it has cost us influence and it has cost us self-respect.”

Mr Farage insisted it was possible for several Ukip MPs to be elected at next year’s general election, but urged his party to focus first on the European elections.

To laughter from activists, he mocked the idea his party was a “splinter group” of the Conservatives and that the typical supporter was a “retired half-colonel living on the edge of Salisbury Plain”.

He said: “One fifth of our voters are people who would be described as non-voters, people who haven’t voted for 20 years, in some cases people who have never voted in their lives and they are going out and voting Ukip.

“I think we should be very proud of the fact we are re-engaging people back in British democracy, I really do.”

He also launched a staunch defence of his candidates and joked about the councillor who claimed gay marriage caused the flooding crisis.