Conservative leader David Cameron took the election fight to Nigel Farage and Ukip today, urging voters to support the party of "the answer" rather than "anger".
Mr Cameron said Ukip, which is expected to do well in the European elections later this month, was a threat to the future of the country because Mr Farage's answer to Europe was to "give up" having taken a "pessimistic view of Britain and the world".
"I know people are frustrated with their politicians, sometimes angry that we haven't taken more steps to deal with these issues, but what we've got to have in our country is the politics of the answer rather than politics of anger," Mr Cameron said.
"Because what we've got to do is fix these problems.
"Fix our welfare system so it rewards the hard working; fix the immigration system so it benefits the whole of our country; get our taxes down so we see living standards rise.
"Those are the things I am focused on because they are the politics of the answer, not the politics of anger.
"It's going to be tough in these European election campaigns to get those points across but in the end if we really want to sort out these problems we need people who have the policies, the answers, the ability to get stuck in and sort these problems out.
"Not simply people who stand up and make an attractive sounding protest."
The Prime Minister spoke out against Mr Farage and his party during a visit to engineering firm Renishaw in the ultra-marginal Conservative seat of Stroud in Gloucestershire.
Tory MP Neil Carmichael will defend a majority of just 1,299 at next year's General Election from challenger, the area's former Labour MP David Drew.
Mr Cameron said Mr Farage was "wrong" on a whole range of policies.
"I just think he's wrong," the Prime Minister said.
"The idea of just turning your back on the world and saying 'We're going to try and build fortress Britain, we're going to leave Europe and shut the door to anyone coming in...' I think is a totally unrealistic and pessimistic vision about what this country can achieve.
"I also don't agree with Labour and the Liberal Democrats, who think everything is right about Europe and we just have to take it as it comes.
"I think the best thing for Britain to do is to engage with the world and try and make changes where we think changes are needed."
Mr Cameron said Britain benefited from membership of the EU because the country was a trading nation.
"We don't just want those markets open, we want a say in what the rules are and that's what membership of the European Union gives us," he said.
"That's a good thing but there are things about Europe we don't like.
"There's too much interference, there's too much regulation, there's not enough emphasis on competitiveness and it costs too much money.
"We need to change those things.
"My message to anyone thinking of voting for Nigel Farage is: Don't give up on Britain in the world. Give us a chance to get in there, negotiate a better deal for Britain and, with me in charge, you will get a referendum before the end of 2017 where the British people can decide: Do we stay in this reformed organisation or do we leave?
"Is he a threat to our economy? Yes, he is, because we are a trading nation and his answer is to give up.
"Is he a threat to me and my party? Politics is about choice. We're in competitive elections and I am going to try and get out around the country and convince people: Don't give up, don't take a pessimistic view of Britain and the world.
"We've shown we can turn around Britain and the economy, we've shown we can create jobs, we've shown we can compete with the world, we've shown the world we can put on the brilliant Olympics.
"So let's be optimistic about what Britain can achieve in the world, rather than give up.
"If people hear that message there is a good chance they will rally to it."
Mr Cameron said the Ukip leader would "turn his back on the world" if given the chance and rejected the call to have an in/out referendum on membership of the EU now.
"We would really be offering people two unacceptable choices: Stay in Europe with everything as it is now, or leave altogether and give up on Britain's trading relationships," the Prime Minister said.
"I don't want to give that choice because Britain should have a better choice."
Mr Cameron also lambasted Mr Farage's immigration policy.
"It's very easy to go around and just say 'Stop everyone coming in', put up the fortress, turn your back on the world and pretend a country like Britain can live like that," he said.
"We can't. We are a trading country. We need to have people coming here and studying, we need people to come and work in businesses, legitimately, just as we go and work in businesses overseas.
"We are never going to succeed if we say all immigration is bad; it isn't, but what we need is the right sort of immigration and carefully controlled immigration and very clearly we need less immigration.
"It got too high over the last decade. Net immigration was 200,000 a year; two million across a decade.
"That's too high and has got to be brought down. Using our borders we are bringing the level of immigration down.
"But we need a sensible, proper, grown-up set of policies and a debate rather than a set of slogans with no answers."
Mr Cameron said the Coalition had made some difficult choices in the past four years but was "on track to finish the plan".
"Trying to turn our economy around and make Britain a success story is the most important thing this Government is doing," he said.
"We have a long-term economic plan to recover from the difficulties we had between 2008 and 2010 in that great recession.
"That plan is not finished but it is on track. We said we would cut the deficit - it is down by a third; not enough, we need to go further, but we are making progress in dealing with our debts.
"We said we wanted to get more people into work. Compared to when I became Prime Minister there are 1.5 million people in work. Unemployment is still too high but that is still good progress.
"We said we wanted to cut people's taxes to give them more of their money to spend as they choose.
"We have now got to a situation where you can earn £10,000 without paying any income tax. I hope we can do more but again, that is progress.
"We said we wanted the right schools and qualifications for our children. Again, there is more work to be done but we've trained 1.7 million apprentices this Parliament and hopefully we can get to 2 million.
"That's progress but, again, more to be done.
"We said we wanted to sort out our welfare and immigration systems, so that they are fair and they back hard-working people. We've capped welfare and we've cut immigration. Again, more to be done but the plan is on track.
"That's the message I want to give today. We have a plan. If we stick to this plan and see through this plan, there is no reason why Britain cannot be a success story in the 21st century and that all of our people can't benefit from that success."