Nigel Farage has pledged to follow the example of Paddy Ashdown and to establish "clusters of councillors" around the country elected on the challenging first-past-the-post system as a first step to winning parliamentary seats at future general elections.

In a Guardian interview, the Ukip leader said people would vote for the "real thing" on Europe and immigration rather than support David Cameron who is occupying "our turf" under the influence of the Tory strategist Lynton Crosby.

Farage admitted that his party is experiencing something of a "lull" but insisted that it was on course to win next year's European parliamentary elections and to deepen its presence in council chambers.

Ukip has seen its support drop in recent months after a breakthrough in the English local elections in May when it won 23% of the vote. A Guardian/ICM poll earlier this month placed Ukip on 7%, compared with 18% shortly after the local election results, with most of its support shifting to the Conservatives.

The Ukip leader said he did not accept the poll findings, saying that other recent polls had put the party on between 18 and 20%, though he conceded that support for his party may dip temporarily. He said: "Even if Ukip does soften a bit in the polls over the summer that would hardly be a surprise. We are, after all, a campaigning party and we are in a bit of a lull at the moment."

Farage said Ukip would gear up by the time of the European parliamentary and local elections which will both be held on 22 May next year. The party is widely expected to perform strongly in the European elections – it came second behind the Tories in 2009 on 16.5% of the vote – and Farage hopes to use its success to improve his party's performance in the local elections on the same day.

But the Ukip leader has ambitions that go way beyond England's town halls as he said he hopes to follow in the footsteps of Ashdown, who steadily built up the Lib Dem parliamentary presence after grassroots success in local elections.

In his first general election outing as Lib Dem leader in 1992, Ashdown won 20 seats on 17.8% of the vote. By 1997 Ashdown more than doubled the number of Lib Dem MPs – to 46 – while the party's share of the vote fell by one point to 16.8%.

Farage said: "We have not just to win the European elections next year. The clever thing is there are over 5,000 council seats up for grabs on the same day as the European elections. What Ukip needs to do is to win significant numbers of seats at local government level and then to follow the model that Paddy Ashdown set for the Lib Dems."

He said that the party's aspiration was to establish "a cluster of councillors that have won under first past the post in a parliamentary constituency" which would send a signal to voters in the area that "this isn't a wasted vote, these guys have got a chance".

That would be a precursor to "ruthlessly target" the seats that Ukip would intend to challenge for in the expected 2015 election. "We have got a long way to go. But, my goodness me, in this year we have made some progress," Farage added.

Farage's remarks about building up a base from councillors elected on the first-past-the-post system imply he is focused on England. Councils are elected by proportional representation in Scotland.

The party leader was scathing about the prime minister as the Tories occupy territory – on immigration and Europe – that had been claimed by Ukip. "It is very interesting to see the influence of Lynton Crosby which is now enormous. I don't think any of these are Cameron's ideas himself."

Arguing that the Conservative leader had changed tack over the years, Farage said: "After all he has led the party since 2005. He wanted it to be the greenest party ever, one that didn't bang on about Europe and tried to bury the immigration debate under the carpet. He is now attempting to talk to the voters on our turf. The trouble is when people look at it they are not going to believe him and many people will say we may as well vote for the real thing."

Farage is not softening his rhetoric on immigration as he says "enough is enough" and castigates the late Enoch Powell for making it difficult to debate immigration after his infamous Rivers of Blood speech in 1968. He said: "The Powell speech was a disaster. Everybody ran scared of discussing this for decades. Now, I think what Ukip has done is to help make immigration a sensible, moderate, realistic, mainstream debate."

Wading further into controversial territory, Farage argued the issue would become a problem for the prime minister because of changes to European migration laws: "I don't think it is inflammatory to say we should not be opening up our jobs market and our entire social security system to Romania and Bulgaria on 1 January next year.

"If they do come in very large numbers and if the current crime wave we are experiencing in London from Romanians – and I am sorry if this is unpleasant but it is true, all backed up by Metropolitan Police figures – if that continues then I think Mr Cameron can say what he likes about immigration, but he could be in some very big trouble on this."

The Ukip leader also said his party cannot afford a repeat of the 2010 general election when Lord Pearson of Rannoch, its then leader, did not know what was in the manifesto. "Poor old Malcolm Pearson he had a bit of a problem last time. It was like a Not the Nine O'Clock News sketch. Jon Sopel [BBC presenter] asked him the question and he said: gosh you've got me there old boy.

"That won't be happening again. We got that wrong. Our manifesto last time was nearly 500 pages long. It was a horlicks. That is not going to happen."

Farage argued that Ukip has "established itself" in policies beyond its traditional areas of Europe and immigration to education, energy policy and championing small businesses. "We have been broadening over the course of the last few years. We are not there yet."

He endorsed an idea proposed by party deputy leader Godfrey Bloom that the party could buy policies from centre right thinktanks. "Why not?" Farage asked. "If somebody else out there has produced brilliant research, has got a lot more money to do this stuff then when [journalists] ask me a question about our economic policy I say: that is our policy but look who else agrees with it. "

Farage also joked that he will not try to attract publicity as he did on the day of the general election in 2010 when his light aircraft crashed after a Ukip banner became tangled up with the tailfin. He said: "No more stunts, no more aeroplanes, no more stupidity. I am going to be older and wiser."

However, he indicated that he might struggle with adopting a lower campaigning profile: "If you believe that you'll believe anything."